Root Zone LGR for script: Lao (Laoo) rz-lgr-5-lao-script-26may22-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 2022-05-26
LGR Version 5 (Root Zone LGR for the Lao Script)
Language und-Laoo (Lao Script)
Scope domain: "." (Root)
Unicode Version 11.0.0

Table of Contents


Root Zone Label Generation Rules for the Lao Script


This file contains Label Generation Rules (LGR) for the Lao script for the Root Zone. For more details on this LGR and additional background on the script, see “Proposal for a Lao Script Root Zone LGR” [Proposal-Lao]. This file is one of a set of LGR files that together form an integrated LGR for the DNS Root Zone [RZ-LGR-5]. The format of this file follows [RFC 7940].


In addition to the 51 code points according to Section 5 “Repertoire” in [Proposal-Lao], the sequence 0EB2 0EB0 has been defined to facilitate implementation of WLE rule follows-vafter-context as a context rule. The repertoire only includes code points used by languages that are actively written in the Khmer script. The repertoire is based on [MSR-5], which is a subset of [Unicode 11.0].

As part of the Root Zone, this LGR includes neither decimal digits nor the HYPHEN-MINUS.

Each code point is tagged with the script or scripts with which the code point is used, one or more other character categories, and one or more references documenting sufficient justification for inclusion in the repertoire; see “References” below. Comments identify the language using the code point.


According to Section 6, “Variants” in [Proposal-Lao], this LGR defines no variants.

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 (ໆ) 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]).

Whole Label Evaluation (WLE) and Context Rules

Default Whole Label Evaluation Rules and Actions

The LGR includes the set of required default WLE rules and actions applicable to the Root Zone and defined in [MSR-5]. They are marked with ⍟. The default prohibition on leading combining marks is equivalent to ensuring that a label only starts with a consonant or vowel-before.

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:

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

Methodology and Contributors

The Root Zone LGR for the Lao script was developed by the Lao Generation Panel. For methodology and contributors, see Sections 4 and 8 in [Proposal-Lao], as well as [RZ-LGR-5-Overview].


The following general references are cited in this document:

Integration Panel, “Maximal Starting Repertoire — MSR-5 Overview and Rationale”, 24 June 2021,
Lao Generation Panel, “Proposal for Lao Script Root Zone LGR”, Version 3.1,
[RFC 7940]
Davies, K. and A. Freytag, “Representing Label Generation Rulesets Using XML”, RFC 7940, August 2016,
Integration Panel, “Root Zone Label Generation Rules (RZ LGR-5): Overview and Summary”, 26 May 2022,
Integration Panel, “Root Zone Label Generation Rules (RZ-LGR-5)”, 26 May 2022 (XML),
non-normative HTML presentation:
[Unicode 11.0]
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 Root Zone please see details in the Table of References below. Reference [0] refers to the Unicode Standard version in which corresponding code points were initially encoded. References [201], [202], [203], [204], 205], [206], & [207] correspond to sources given in [Proposal-Lao] justifying the inclusion of or classification for the corresponding code points. Entries in the table may have multiple source reference values.


Repertoire Summary

Number of elements in repertoire 52
Number of code points 51
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.

See also the legend provided below the table.

Glyph Script Name Ref Tags Required Context Comment
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


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.
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 Sets

This LGR does not specify any variants.

Classes, Rules and Actions

Character Classes

Number of named classes 6
Implicit (except script) 3
Implict defined by script tag 1

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
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 51 {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}   Any character tagged as Lao


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 10
Used to trigger actions 1
Used as context rule (C) 8
Anchored context rules 8
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}]]       Default WLE rule matching labels with leading combining marks ⍟
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


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.
(... | ...) - 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.
*, +, ?, {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   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 at least one variant is in {blocked} blocked   any variant label containing blocked variants is blocked ⍟
4 if each variant is in {allocatable} allocatable   variant labels with all variants allocatable are allocatable ⍟
5 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.

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 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]