Reference LGR for script: Lao (Laoo) lgr-second-level-lao-script-24jan24-en

This document is mechanically formatted from the above XML file for the LGR. It provides additional summary data and explanatory text. The XML file remains the sole normative specification of the LGR.

Date 2024-01-24
LGR Version 3 (Second Level Reference LGR)
Language und-Laoo (Lao Script)
Unicode Version 11.0.0



  • These instructions cover how to adopt an LGR based on this reference LGR for a given zone and how to prepare the file for deposit in the IANA Repository of IDN Practices.
  • As described the IANA procedure
    an LGR MUST contain the following elements in its header:
    • Script or Language Designator (see below for guidance)
    • Version Number (this must increase with each amendment to the LGR, even if the updates are limited to the header itself)
    • Effective Date (the date at which the policy becomes applicable in operational use)
    • Registry Contact Details (contact name, email address, and/or phone number)
  • The following information is optional:
    • Document creation date
    • Applicable Domain(s)
    • Changes made to the Reference LGR before adopting

Please add or modify the following items in the XML source code for this file before depositing the document in the IANA Repository.

Meta Data

Note: version numbers start at 1. RFC 7940 recommends using simple integers. The version comment is optional, please replace or delete the default comment. Version comments may be used by some tools as part of the page header.

<version comment="[Please replace (or delete) the optional comment]">[Please fill in version number, starting at 1]</version>

<date>[Please fill in with publication date, in YYYY-MM-DD format]</date>

<validity-start>[Please fill in effective date, in YYYY-MM-DD format]</validity-start>

Note: the scope element may be repeated, so that the same document can serve for multiple domains.

<scope type="domain">[Please provide, in ".domain" format]</scope>

Registry Contact Information:

Please fill in the Registry Contact Details.

Change History

If you made technical modifications to the LGR, please summarize them in the Change History (and also note the details in the appropriate section of the description).


Registry Contact Details

Label Generation Rules for the Lao Script


This document specifies a set of Label Generation Rules (LGR) for the Lao script for the second level domain or domains identified above. The starting point for the development of this LGR can be found in the related Root Zone LGR [RZ-LGR-Laoo]. The format of this file follows [RFC 7940]. This LGR is adapted from the “Reference LGR for the Second Level for the Lao Script” [Ref-LGR-und-Laoo], for details, see Change History below.

For details and additional background on the Lao script, see “Proposal for a Lao Script Root Zone LGR” [Proposal-Lao].


The repertoire contains 51 code points for letters; in addition, the sequence U+0EB2 U+0EB0 າະ has been defined to facilitate implementation of WLE rule follows-vbefore-consonant-cluster as a context rule. The repertoire only includes code points used by languages that are actively written in the Lao script. The repertoire is a subset of [Unicode 11.0.0]. For details, see Section 5, “Repertoire” in [Proposal-Lao]. (The proposal cited has been adopted for the Lao script portion of the Root Zone LGR.)

For the second level, the repertoire has been augmented with the ASCII digits, U+0030 0 to U+0039 9, Lao digits, U+0ED0 to U+0ED9 , and U+002D - HYPHEN-MINUS, for a total of 73 repertoire elements.

Repertoire Listing: Each code point or range is tagged with the script or scripts with which the code point is used, one or more tag values denoting character category, and one or more references documenting sufficient justification for inclusion in the repertoire, see “References” below. Comments provide alternate names for some code points.


The variants defined in this LGR are limited to those required for use in zones not shared with any other script. However, because it does not share cross-script variants with other script LGRs, this LGR can be mixed easily with other LGRs in the same zone.

This LGR defines no variants for letters. See Section 6, “Variants” in [Proposal-Lao].

Digit Variants: All Lao digits are treated as semantic variants of the corresponding common (ASCII) digits. By transitivity, they are also semantic variants of any native digits in scripts that also include the common digits. Such variant relations are deemed to exist implicitly by transitivity but are not listed explicitly in each reference LGR. Instead, if needed, they are applied by using the Common LGR in label processing.

In particular, Lao digit ZERO is a cross-script homoglyph or near homoglyph of digit ZERO in many other scripts; these are already implicit semantic variants by transitivity and therefore not listed here.

There is a strong resemblance between Thai and Khmer digits, as well as with certain Lao digits.

To keep digit variant sets manageable in zones where multiple scripts are present, no attempt has been made at identifying cross-script variants among digits of different numeric value or between a digit in one script and a letter in another, such as between digit zero and Latin letter ‘o’. Other mechanisms may be required to prevent homograph labels.

Variant Disposition: All variants are of type “blocked”, making labels that differ only by these variants mutually exclusive: whichever label containing either of these variants is chosen earlier would be delegated, while any other equivalent labels should be blocked. There is no preference among these labels.

This LGR does not define allocatable variants.

The specification of variants in this LGR follows the guidelines in [RFC 8228].

Character Classes

Consonants: In regular syllables, consonants occur in limited combinations. However, arbitrary combinations are used for acronyms. The LGR therefore considers the restriction on syllabic combinations a matter of spelling and does not enforce them. Consonants may be followed by a semi-consonant mark. Some consonants have been given the tag “Cf”, which indicates final consonants. See Section 5, “Consonants” in [Proposal-Lao].

Vowels: Vowels are divided into vowel-above, vowel-before, vowel-below and vowel-after so as to enforce some of the syllable structure using context rules. However, many details have been considered spelling issues and, for simplification, are not modeled in this LGR. See Section 5 in [Proposal-Lao].

Semi-consonant: The character U+0EBC  ຼ  LAO SEMIVOWEL SIGN LO follows consonants (see Section 5 in [Proposal-Lao]).

Tone-mark: Any of four tone marks can follow a consonant or vowel-above or vowel-below (see Section 5 in [Proposal-Lao]).

Signs: The character U+0ECC  ໌  LAO CANCELLATION MARK follows a final consonant (Cf). The character U+0EC6 LAO KO LA is a repetition mark that can only occur up to 3 times at the end of the label (See Section 5 in [Proposal-Lao]).

Lao Digits: U+0E50 to U+0E59 are a set of Lao-specific digits. They are used in alternation with the European (common) digits.

Common Digits: U+0030 0 to U+0039 9 are the set of digits from the ASCII range.

Whole Label Evaluation (WLE) and Context Rules

Common Rules

The LGR includes the rules and actions to implement the following restrictions, some of which are mandated by the IDNA protocol. They are marked with ⍟ and included here by default.

  • Hyphen Restrictions — restrictions on the allowable placement of hyphens (no leading/ending hyphen and no hyphen in positions 3 and 4). These restrictions are described in Section of RFC 5891 [150]. They are implemented here as context rule on U+002D (-) HYPHEN-MINUS.
  • Leading Combining Marks — restrictions on the allowable placement of combining marks (no leading combining mark). This rule is described in Section of RFC 5891 [150].
  • Digit-mixing — no mixing between different digit sets (European and Lao digits) is allowed; implemented here as a WLE rule with associated action.

Default Actions

This LGR includes the complete set default actions for LGRs as well as the action needed to invalidate labels with misplaced combining marks. They are marked with ⍟. For a description see [RFC 7940] and [150]. An additional action is triggered by mixed digit labels.

Lao-specific Rules

Rules provided in the LGR as described in Section 7 of [Proposal-Lao] reasonably restrict labels so that they conform to Lao syllable structure. These constraints are presented exclusively as context rules.

The rules are:

  • follows-consonant — A context rule for semi-consonant. See Section 7 in [Proposal-Lao]. (WLE Rule 1)
  • precedes-consonant — A context rule for vowel-before. See Section 7 in [Proposal-Lao]. (WLE Rule 2)
  • follows-main-consonant — A context rule for vowel-below, and vowel-above. See Section 7 in [Proposal-Lao]. (WLE Rule 3)
  • follows-C-tonemark-vabove — A context rule for vowel-after. See Section 7 in [Proposal-Lao]. (WLE Rule 4)
  • follows-vbefore-consonant-cluster — A context rule for a vowel-after sequence. It incorporates consonant-cluster. See Section 7 in [Proposal-Lao]. (WLE Rule 5)
  • follows-C-vabove-vbelow — A context rule for tone mark. See Section 7 in [Proposal-Lao]. (WLE Rule 6)
  • follows-Cf — A context rule for U+0ECC  ໌  LAO CANCELLATION MARK. See Section 7 in [Proposal-Lao]. (WLE Rule 7)
  • repetition-mark-limit — A rule that limits the occurrence of U+0EC6 LAO KO LA at the label end. See Section 7 in [Proposal-Lao]. (WLE Rule 8)

No context rules apply to “consonant” code points. For discussion, see Section 5.1, “Consonants” in [Proposal-Lao].

Methodology and Contributors

The LGR in this document has been adapted from the corresponding Reference LGR for the Second Level. The Second Level Reference LGR for the Lao Script was developed by Michel Suignard and Asmus Freytag, based on the Root Zone LGR for the Lao script and information contained or referenced therein; see [RZ-LGR-Laoo]. Suitable extensions for the second level have been applied according to the [Guidelines] and with community input. The original proposal for a Root Zone LGR for the Lao script, that this LGR is based on, was developed by the Lao Generation Panel. For more information on methodology and contributors to the underlying Root Zone LGR, see Sections 4 and 8 in [Proposal-Lao], as well as [RZ-LGR-Overview].

Changes from Version Dated 15 December 2020

Comments for Lao digits have been corrected.

Changes from Version Dated 22 April 2021

Unicode Version has been updated.

Changes from Version Dated 24 January 2024

Adopted from the Second Level Reference LGR for the Lao Script [Ref-LGR-und-Laoo] without normative changes.


The following general references are cited in this document:

ICANN, “Guidelines for Developing Reference LGRs for the Second Level”, (Los Angeles, California: ICANN, 27 May 2020),
Internet Corporation for Assigned Names and Numbers, (ICANN),“Reference Label Generation Rules (LGR) for the Second Level: Overview and Summary” (PDF), (Los Angeles, California: ICANN, 24 January 2024),
Lao Generation Panel, “Proposal for Lao Script Root Zone LGR”,
ICANN, Second Level Reference Label Generation Rules for the Lao Script (und-Laoo), 24 January 2024 (XML)
non-normative HTML presentation:
[RFC 7940]
Davies, K. and A. Freytag, “Representing Label Generation Rulesets Using XML”, RFC 7940, August 2016,
[RFC 8228]
A. Freytag, “Guidance on Designing Label Generation Rulesets (LGRs) Supporting Variant Labels”, RFC 8228, August 2017,
Integration Panel, “Root Zone Label Generation Rules (RZ LGR-5): Overview and Summary”, 26 May 2022 (PDF),
ICANN, Root Zone Label Generation Rules for the Lao Script (und-Laoo), 26 May 2022 (XML)
[Unicode 11.0.0]
The Unicode Consortium. The Unicode Standard, Version 11.0.0, (Mountain View, CA: The Unicode Consortium, 2018. ISBN 978-1-936213-19-1)

For references consulted particularly in designing the repertoire for the Lao Script for the second level please see details in the Table of References below.

Reference [0] refers to Unicode Standard version in which corresponding code points were initially encoded. References [201], [202], [203], [204], [205], [206], & [207] correspond to sources justifying the inclusion of or classification for the corresponding code points. Entries in the table may have multiple source reference values. In the listing of whole label evaluation and context rules, reference [150] indicates the source for common rules.


Repertoire Summary

Number of elements in repertoire 73
Number of code points
for each script
Lao 61
Common 11
Number of code points 72
Number of sequences 1
Longest code point sequence 2

Repertoire by Code Point

The following table lists the repertoire by code point (or code point sequence). The data in the Script and Name column are extracted from the Unicode character database. Where a comment in the original LGR is equal to the character name, it has been suppressed.

For any code point or sequence for which a variant is defined, additional information is provided in the Variants column. See also the legend provided below the table.

Glyph Script Name Ref Tags Required Context Variants Comment
U+002D - Common HYPHEN-MINUS [0]   not: hyphen-minus-disallowed  
U+0030 0 Common DIGIT ZERO [0] Common-digit   set 1
U+0031 1 Common DIGIT ONE [0] Common-digit   set 2
U+0032 2 Common DIGIT TWO [0] Common-digit   set 3
U+0033 3 Common DIGIT THREE [0] Common-digit   set 4
U+0034 4 Common DIGIT FOUR [0] Common-digit   set 5
U+0035 5 Common DIGIT FIVE [0] Common-digit   set 6
U+0036 6 Common DIGIT SIX [0] Common-digit   set 7
U+0037 7 Common DIGIT SEVEN [0] Common-digit   set 8
U+0038 8 Common DIGIT EIGHT [0] Common-digit   set 9
U+0039 9 Common DIGIT NINE [0] Common-digit   set 10
U+0E81 Lao LAO LETTER KO [0], [201], [204] Cf, consonant     Lao
U+0E82 Lao LAO LETTER KHO SUNG [0], [201], [204] consonant     Lao
U+0E84 Lao LAO LETTER KHO TAM [0], [201], [204] consonant     Lao
U+0E87 Lao LAO LETTER NGO [0], [201], [204] Cf, consonant     Lao
U+0E88 Lao LAO LETTER CO [0], [201], [204] consonant     Lao
U+0E8A Lao LAO LETTER SO TAM [0], [201], [204] Cf, consonant     Lao
U+0E8D Lao LAO LETTER NYO [0], [201], [204] Cf, consonant     Lao
U+0E94 Lao LAO LETTER DO [0], [201], [204] Cf, consonant     Lao
U+0E95 Lao LAO LETTER TO [0], [201], [204] consonant     Lao
U+0E96 Lao LAO LETTER THO SUNG [0], [201], [204] consonant     Lao
U+0E97 Lao LAO LETTER THO TAM [0], [201], [204] Cf, consonant     Lao
U+0E99 Lao LAO LETTER NO [0], [201], [204] Cf, consonant     Lao
U+0E9A Lao LAO LETTER BO [0], [201], [204] Cf, consonant     Lao
U+0E9B Lao LAO LETTER PO [0], [201], [204] consonant     Lao
U+0E9C Lao LAO LETTER PHO SUNG [0], [201], [204] consonant     Lao
U+0E9D Lao LAO LETTER FO FON [0], [201], [204] consonant     = lao letter fo sung; Lao
U+0E9E Lao LAO LETTER PHO TAM [0], [201], [204] consonant     Lao
U+0E9F Lao LAO LETTER FO FAY [0], [201], [204] Cf, consonant     = lao letter fo tam; Lao
U+0EA1 Lao LAO LETTER MO [0], [201], [204] Cf, consonant     Lao
U+0EA2 Lao LAO LETTER YO [0], [201], [204] consonant     Lao
U+0EA3 Lao LAO LETTER RO [0], [204] Cf, consonant     = lao letter lo rada; Lao
U+0EA5 Lao LAO LETTER LO [0], [201], [204] Cf, consonant     = lao letter lo ling; Lao
U+0EA7 Lao LAO LETTER WO [0], [201], [204], [205] Cf, consonant     Lao
U+0EAA Lao LAO LETTER SO SUNG [0], [201], [204] Cf, consonant     Lao
U+0EAB Lao LAO LETTER HO SUNG [0], [201], [204] consonant     Lao
U+0EAD Lao LAO LETTER O [0], [201], [204], [205] consonant     Lao
U+0EAE Lao LAO LETTER HO TAM [0], [201], [204] consonant     Lao
U+0EB0 Lao LAO VOWEL SIGN A [0], [201], [205], [206] vowel-after follows-C-tonemark-vabove   Lao
U+0EB1  ັ Lao LAO VOWEL SIGN MAI KAN [0], [201], [205], [206] vowel-above follows-main-consonant   Lao
U+0EB2 Lao LAO VOWEL SIGN AA [0], [201], [205], [206] vowel-after follows-C-tonemark-vabove   Lao
U+0EB2 U+0EB0 າະ {Lao} LAO VOWEL SIGN AA + LAO VOWEL SIGN A [205] [vowel-after] + [vowel-after] follows-vbefore-consonant-cluster   Lao
U+0EB4  ິ Lao LAO VOWEL SIGN I [0], [201], [205], [206] vowel-above follows-main-consonant   Lao
U+0EB5  ີ Lao LAO VOWEL SIGN II [0], [201], [205], [206] vowel-above follows-main-consonant   Lao
U+0EB6  ຶ Lao LAO VOWEL SIGN Y [0], [201], [205], [206] vowel-above follows-main-consonant   Lao
U+0EB7  ື Lao LAO VOWEL SIGN YY [0], [201], [205], [206] vowel-above follows-main-consonant   Lao
U+0EB8  ຸ Lao LAO VOWEL SIGN U [0], [201], [205], [206] vowel-below follows-main-consonant   Lao
U+0EB9  ູ Lao LAO VOWEL SIGN UU [0], [201], [205], [206] vowel-below follows-main-consonant   Lao
U+0EBB  ົ Lao LAO VOWEL SIGN MAI KON [0], [205] vowel-above follows-main-consonant   Lao
U+0EBC  ຼ Lao LAO SEMIVOWEL SIGN LO [0], [201], [205], [206] semi-consonant follows-consonant   = lao semiconsonant lo; Lao
U+0EBD Lao LAO SEMIVOWEL SIGN NYO [0], [201], [205] vowel-after follows-C-tonemark-vabove   = lao semivowel ia; Lao
U+0EC0 Lao LAO VOWEL SIGN E [0], [201], [205], [206] vowel-before precedes-consonant   Lao
U+0EC1 Lao LAO VOWEL SIGN EI [0], [201], [205], [206] vowel-before precedes-consonant   Lao
U+0EC2 Lao LAO VOWEL SIGN O [0], [201], [205], [206] vowel-before precedes-consonant   Lao
U+0EC3 Lao LAO VOWEL SIGN AY [0], [201], [205], [206] vowel-before precedes-consonant   Lao
U+0EC4 Lao LAO VOWEL SIGN AI [0], [201], [205], [206] vowel-before precedes-consonant   Lao
U+0EC6 Lao LAO KO LA [0], [203] sign repetition-mark-limit   = lao may sam; Lao
U+0EC8  ່ Lao LAO TONE MAI EK [0], [202] tone-mark follows-C-vabove-vbelow   Lao
U+0EC9  ້ Lao LAO TONE MAI THO [0], [202] tone-mark follows-C-vabove-vbelow   Lao
U+0ECA  ໊ Lao LAO TONE MAI TI [0], [202] tone-mark follows-C-vabove-vbelow   Lao
U+0ECB  ໋ Lao LAO TONE MAI CATAWA [0], [202] tone-mark follows-C-vabove-vbelow   = lao tone mai jattawa; Lao
U+0ECC  ໌ Lao LAO CANCELLATION MARK [0], [207] sign follows-Cf   = lao mark mai ka lan; Lao
U+0ECD  ໍ Lao LAO NIGGAHITA [0], [201], [205], [206] vowel-above follows-main-consonant   = lao vowel sign or; Lao
U+0ED0 Lao LAO DIGIT ZERO [0] Lao-digit   set 1  
U+0ED1 Lao LAO DIGIT ONE [0] Lao-digit   set 2  
U+0ED2 Lao LAO DIGIT TWO [0] Lao-digit   set 3  
U+0ED3 Lao LAO DIGIT THREE [0] Lao-digit   set 4  
U+0ED4 Lao LAO DIGIT FOUR [0] Lao-digit   set 5  
U+0ED5 Lao LAO DIGIT FIVE [0] Lao-digit   set 6  
U+0ED6 Lao LAO DIGIT SIX [0] Lao-digit   set 7  
U+0ED7 Lao LAO DIGIT SEVEN [0] Lao-digit   set 8  
U+0ED8 Lao LAO DIGIT EIGHT [0] Lao-digit   set 9  
U+0ED9 Lao LAO DIGIT NINE [0] Lao-digit   set 10  


Throughout this LGR, a code point sequence may be annotated with a string in ALL CAPS that is constructed on the same principle as a name for a Unicode Named Sequence. No claim is made that a sequence thus annotated is in fact a named sequence, nor that the annotation in such case actually corresponds to the formal name of a named sequence.

Code Point
A code point or code point sequence.
The shape displayed depends on the fonts available to your browser.
Shows the script property value from the Unicode Character Database. Combining marks may have the value Inherited and code points used with more than one script may have the value Common. Sequences are annotated with a set of all distinct script values.
Shows the character or sequence name from the Unicode Character Database. Named sequences are listed with their normative names, for ad-hoc sequences the individual names are shown separated by “+”.
Links to the references associated with the code point or sequence, if any.
LGR-defined tag values. Any tags matching the Unicode script property are suppressed in this view. For sequences, the tags for all member code points are shown in [] for information; sequences as such do not have tags.
Required Context
Link to a rule defining the required context a code point or sequence must satisfy. If prefixed by “not:” identifies a context that must not occur.
Link to the variant set the code point or sequence is a member of, except where a coded point or sequence maps only to itself, in which case the type of that mapping is listed.
The comment as given in the XML file. However, if the comment for this row consists only of the code point or sequence name, it is suppressed in this view. By convention, comments starting with “=” denote an alias. If present, the symbol ⍟ marks a default item shared among a set of LGRs.


Variant Set Summary

Number of variant sets 10
Largest variant set 2
Variants by Type
blocked 20

Variant Sets

The following tables list all variant sets defined in this LGR, except for singleton sets. Each table lists all variant mapping pairs of the set; one per row. Mappings are assumed to be symmetric: each row documents both forward (→) and reverse (←) mapping directions. In each table, the mappings are sorted by Source value in ascending code point order; shading is used to group mappings from the same source code point or sequence.

Where the type of both forward and reverse mappings are the same, a single value is given in the Type column; otherwise the types for forward and reverse mappings, as well as comments and references, are listed above one another. For summary counts, both forward and reverse mappings are always counted separately.

In any LGR with variant specifications that are well behaved, all members within each variant set are defined as variants of each other; the mappings in each set are symmetric and transitive; and all variant sets are disjoint.

Common Legend

By convention, the smaller of the two code points in a variant mapping pair.
By convention, the larger of the two code points in a variant mapping pair.
The shape displayed for source or target depends on the fonts available to your browser.
- forward
Indicates that Type, Ref and Comment apply to the mapping from source to target.
- reverse
Indicates that Type, Ref and Comment apply to the reverse mapping from target to source.
- both
Indicates that Type, Ref and Comment apply to both forward and reverse mapping.
The type of the variant mapping, including predefined variant types such as “allocatable” and “blocked”; or any that are defined specifically for this LGR.
One or more reference IDs (optional). A “/” separates references for reverse / forward mappings, if different.
A descriptive comment (optional). A “/” separates comments for reverse / forward mappings, if different.

Variant Set 1 — 2 Members

Source Glyph Target Glyph   Type Ref Comment
0030 0 0ED0 blocked   ASCII digit variant / Lao digit variant

Variant Set 2 — 2 Members

Source Glyph Target Glyph   Type Ref Comment
0031 1 0ED1 blocked   ASCII digit variant / Lao digit variant

Variant Set 3 — 2 Members

Source Glyph Target Glyph   Type Ref Comment
0032 2 0ED2 blocked   ASCII digit variant / Lao digit variant

Variant Set 4 — 2 Members

Source Glyph Target Glyph   Type Ref Comment
0033 3 0ED3 blocked   ASCII digit variant / Lao digit variant

Variant Set 5 — 2 Members

Source Glyph Target Glyph   Type Ref Comment
0034 4 0ED4 blocked   ASCII digit variant / Lao digit variant

Variant Set 6 — 2 Members

Source Glyph Target Glyph   Type Ref Comment
0035 5 0ED5 blocked   ASCII digit variant / Lao digit variant

Variant Set 7 — 2 Members

Source Glyph Target Glyph   Type Ref Comment
0036 6 0ED6 blocked   ASCII digit variant / Lao digit variant

Variant Set 8 — 2 Members

Source Glyph Target Glyph   Type Ref Comment
0037 7 0ED7 blocked   ASCII digit variant / Lao digit variant

Variant Set 9 — 2 Members

Source Glyph Target Glyph   Type Ref Comment
0038 8 0ED8 blocked   ASCII digit variant / Lao digit variant

Variant Set 10 — 2 Members

Source Glyph Target Glyph   Type Ref Comment
0039 9 0ED9 blocked   ASCII digit variant / Lao digit variant

Classes, Rules and Actions

Character Classes

Number of named classes 8
Implicit (except script) 3
Implict defined by script tag 2

The following table lists all named and implicit classes with their definition and a list of their members intersected with the current repertoire (for larger classes, this list is elided).

Name Definition Count Members or Ranges Ref Comment
Cf Tag=Cf 14 {0E81 0E87 0E8A 0E8D 0E94 0E97 0E99-0E9A 0E9F 0EA1 0EA3 0EA5 0EA7 0EAA}   Any Lao final consonant
consonant Tag=consonant 27 {0E81-0E82 0E84 0E87-0E88 0E8A 0E8D 0E94-0E97 0E99-0E9F 0EA1-0EA3 0EA5 0EA7 0EAA-0EAB 0EAD-0EAE}   Any Lao consonant
semi-consonant Tag=semi-consonant 1 {0EBC}   Lao semi-consonant LO
tone-mark Tag=tone-mark 4 {0EC8-0ECB}   Any Lao one mark
vowel-above Tag=vowel-above 7 {0EB1 0EB4-0EB7 0EBB 0ECD}   Any Lao vowel above
vowel-below Tag=vowel-below 2 {0EB8-0EB9}   Any Lao vowel below
common-digits Tag=Common-digit 10 {0030-0039}   Digits from the ASCII range; ⍟
lao-digits Tag=Lao-digit 10 {0ED0-0ED9}   Lao digits
implicit Tag=sign 2 {0EC6 0ECC}   Any character tagged as sign
implicit Tag=vowel-after 3 {0EB0 0EB2 0EBD}   Any character tagged as vowel-after
implicit Tag=vowel-before 5 {0EC0-0EC4}   Any character tagged as vowel-before
implicit Tag=sc:Laoo 61 {0E81-0E82 0E84 0E87-0E88 0E8A 0E8D 0E94-0E97 0E99-0E9F 0EA1-0EA3 0EA5 0EA7 0EAA-0EAB 0EAD-0EAE 0EB0-0EB2 0EB4-0EB9 0EBB-0EBD 0EC0-0EC4 0EC6 0EC8-0ECD 0ED0-...}   Any character tagged as Lao
implicit Tag=sc:Zyyy 11 {002D 0030-0039}   Any character tagged as Common


Members or Ranges
Lists the members of the class as code points (xxx) or as ranges of code points (xxx-yyy). Any class too numerous to list in full is elided with "...".
A named or implicit class defined by all code points that share the given tag value (ttt).
An anonymous class implicitly defined based on tag value and for which there is no named equivalent.

Whole label evaluation and context rules

Number of rules 12
Used to trigger actions 2
Used as context rule (C) 9
Anchored context rules 9
Used only in another rule 1

The following table lists all named rules defined in the LGR and indicates whether they are used as trigger in an action or as context (when or not-when) for a code point or variant.

Name Regular Expression Used as
Anchor Used as
Ref Comment
leading-combining-mark (start)[[\p{gc=Mn}] ∪ [∅=\p{gc=Mc}]]     [150] RFC 5891 restrictions on placement of combining marks ⍟
hyphen-minus-disallowed (((start))← ⚓︎)|(⚓︎ →((end)))|(((start)..\u002D)← ⚓︎)   C [150] RFC 5891 restrictions on placement of U+002D -
follows-consonant ([:consonant:])← ⚓︎   C   WLE Rule 1: A semi-consonant must follow a consonant
precedes-consonant ⚓︎ →([:consonant:])   C   WLE Rule 2: A vowel-before precedes a main consonant cluster
follows-main-consonant ([:consonant:]|[:semi-consonant:])← ⚓︎   C   WLE Rule 3: A vowel-above, and vowel-below follow a main consonant C
follows-C-tonemark-vabove ([:consonant:]|[:semi-consonant:]|[:tone-mark:]|[:vowel-above:])← ⚓︎   C   WLE Rule 4: A vowel-after follows a main consonant, tone-mark or vowel-above
consonant-cluster [:consonant:]{1,2}[:semi-consonant:]?         Defining consonant cluster for WLE Rule 5
follows-vbefore-consonant-cluster (\u0EC0(:consonant-cluster:))← ⚓︎   C   WLE Rule 5: The sequence U+0EB2 U+0EB0 າະ follows a vowel before, and a consonant cluster
follows-C-vabove-vbelow ([:consonant:]|[:semi-consonant:]|[:vowel-above:]|[:vowel-below:])← ⚓︎   C   WLE Rule 6: A tone-mark follows a main consonant, vowel-above or vowel-below
follows-Cf ([:Cf:])← ⚓︎   C   WLE Rule 7: The sign U+0ECC  ໌  can only occur after final consonants
repetition-mark-limit ⚓︎ →(\u0EC6{0,2}(end))   C   WLE Rule 8: The sign U+0EC6 can only occur 0 to 3 times at the end of the label
digit-mixing ([:common-digits:].*[:lao-digits:])|([:lao-digits:].*[:common-digits:])       restrictions on mixing digits


Used as Trigger
This rule triggers one of the actions listed below.
Used as Context
This rule defines a required or prohibited context for a code point C or variant V.
This rule has a placeholder for the code point for which it is evaluated.
Regular Expression
A regular expression equivalent to the rule, shown in a modified notation as noted:
⚓︎ - context anchor
Placeholder for the actual code point when a context is evaluated. The code point must occur at the position corresponding to the anchor. Rules containing an anchor cannot be used as triggers.
(...)← - look-behind
If present encloses required context preceding the anchor.
→(..) - look-ahead
If present encloses required context following the anchor.
(: :) - rule reference
Non-recursive reference to a named rule.
( ) - group
An anonymous nested rule is used to group match operators.
(... | ...) - choice
When there is more than one alternative in a rule, the choices are separated by the alternation operator (...|...).
start or end
(start) matches the start of the label; (end) matches the end of the label.
. - any code point
. matches any code point.
*, +, ?, {n,m} - count operators
* indicates 0 or more, + indicates one or more, and ? indicates up to one instance. {n,m} indicates at least n and at most m instances.
[: :] - named or implicit character set
Reference to a named character set [:name:] or an implicit character set [:tag:]. A leading “^” before name or tag indicates the set complement.
[\p{ }] - property
Set of all characters matching a given value for a Unicode property [\p{prop=val}]. Note: uppercase “\P” defines the complement of a property set.
∪, ∩, ∖, ∆ - set operators
Sets may be combined by set operators ( = union, = intersection, = difference, = symmetric difference).
∅= - empty set
Indicates that the following set is empty because of the result of set operations, or because none of its elements is part of the repertoire defined here. A rule with a non-optional empty set never matches.
⍟ - default rule
Rules marked with ⍟ are included by default and may or may not be triggered by any possible label under this LGR.


The following table lists the actions that are used to assign dispositions to labels and variant labels based on the specified conditions. The order of actions defines their precedence: the first action triggered by a label is the one defining its disposition.

# Condition Rule / Variant Set   Disposition Ref Comment
1 if label matches leading-combining-mark invalid [150] labels with leading combining marks are invalid ⍟
2 if at least one variant is in {out-of-repertoire-var} invalid   any variant label with a code point out of repertoire is invalid ⍟
3 if label matches digit-mixing invalid   a label violating the restriction on digit mixing is invalid
4 if at least one variant is in {blocked} blocked   any variant label containing blocked variants is blocked ⍟
5 if each variant is in {allocatable} allocatable   variant labels with all variants allocatable are allocatable ⍟
6 if any label (catch-all)   valid   catch all (default action) ⍟


{...} - variant type set
In the “Rule/Variant Set” column, the notation {...} means a set of variant types.
⍟ - default action
Actions marked with ⍟ are included by default and may or may not be triggered by any possible label under this LGR.

Note: The following variant types are used in one or more actions, but are not defined in this LGR: allocatable, out-of-repertoire-var. This is not necessarily an error.

Table of References

The following lists the references cited for specific code points, variants, classes, rules or actions in this LGR. For General references refer to the References section in the Description.

[0] The Unicode Standard, Version 1.1
Any code point originally encoded in Unicode 1.1
[201] Lao grammar book published by the Ministry of Education in 1967, see Appendix B, Figure 1 in [Proposal-Lao]
[202] Lao grammar book published by the Ministry of Education in 1967, see Appendix B, Figure 2 in [Proposal-Lao]
[203] Lao grammar book published by the Ministry of Education in 1967, see Appendix B, Figure 3 in [Proposal-Lao]
[204] Lao grammar book published by the Ministry of Education in 2000, see Appendix B, Figure 4 in [Proposal-Lao]
[205] Lao grammar book published by the Ministry of Education in 2000, see Appendix B, Figure 5 in [Proposal-Lao]
[206] Lao grammar book published by the Ministry of Education in 2000, see Appendix B, Figure 6 in [Proposal-Lao]
[207] Lao grammar 1935, see Appendix B, Figure 7 in [Proposal-Lao]
[150] RFC 5891, Internationalized Domain Names in Applications (IDNA): Protocol