Reference LGR for script: Tamil (Taml) lgr-second-level-tamil-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 2 (Second Level Reference LGR)
Language und-Taml (Tamil 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 Tamil Script


This document specifies a set of Label Generation Rules (LGR) for the Tamil 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-Taml]. The format of this file follows [RFC 7940]. This LGR is adapted from the “Reference LGR for the Second Level for the Tamil Script” [Ref-LGR-und-Taml], for details, see Change History below.

For details and additional background on the Tamil script, see “Proposal for a Tamil Script Root Zone Label Generation Rule-Set (LGR)” [Proposal-Tamil].


The repertoire contains 48 code points for letters and 4 sequences used to write the Tamil language. The repertoire is a subset of [Unicode 11.0.0]. For details, see Section 5, “Repertoire” in [Proposal-Tamil]. (The proposal cited has been adopted for the Tamil 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, plus U+002D - HYPHEN-MINUS, for a total of 63 repertoire elements.

Any code points outside the Tamil Script repertoire that are targets for out-of-repertoire variants would be included here only if the variant is listed in this file. In this case they are identified as a reflexive (identity) variant of type “out-of-repertoire-var”. Whether or not they are listed, they do not form part of the repertoire.

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. As such, this LGR does not define cross-script variants. However, using this LGR concurrently with any LGR for Malayalam in the same zone will create potential cross-script issues. For details, see Section 6, “Variants” in [Proposal-Tamil]. Mitigation of these cross-script variants can be addressed by using the Common LGR. For details, see Section 3, “Use of Multiple Reference LGRs in the Same Zone” in [Level-2-Overview]. In addition to variants defined by this LGR, the full variant information related to this script and required for concurrent use with the Malayalam LGR(s) can be found in the following LGR: [Ref-LGR-Tamil-Full-Variant-Script]

This LGR defines four sequences as in-script variants. Two of them are variants to single code points; the other two are variants of each other; all defined variants look exactly alike and can cause confusion even to a careful observer. For detais, see Section 6, “Variants” in [Proposal-Tamil].

Digit Variants: The Tamil reference LGR does not include native digits, so there are no semantic variants defined.

However, some Tamil letters are homoglyphs of native digits. For example, U+0BE7 TAMIL DIGIT ONE and U+0BED TAMIL DIGIT SEVEN are homoglyphs of U+0B95 TAMIL LETTER KA and U+0B8E TAMIL LETTER E respectively.

Should an extension be contemplated that adds native digits, these might require variant relations. At the same time, however, any native digits would normally be semantic variants of the ASCII digits. In any zone containing multiple scripts, these two types of variant relation for digits may lead to complication once transitivity is applied.

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].

For historical reasons, there are two sequences that both represent the same akshar (Shri) with exactly the same rendered form. These two sequences are thus semantically identical and users may choose either one, except that a single label must use one of these forms consistently. This variant pair is thus being defined as “allocatable” variant. (For more details see Section 6.1 in [Proposal-Tamil].)

Character Classes

Tamil is an alphasyllabary and the heart of the writing system is the akshar. This is the unit which is instinctively recognized by users of the script. As encoded, the writing system of Tamil is composed of Consonants, the Implicit Vowel Killer: Halant, Vowels and Visarga/Aytham.

Consonants: More details in Section 3.3.1, “The Consonants” in [Proposal-Tamil].

Halant / Virama: All consonants contain an implicit vowel /a/. A special sign is needed to denote that this implicit vowel is stripped off. This is known as the Pulli and encoded as U+0BCD  ்  TAMIL SIGN VIRAMA. The virama thus joins two adjacent consonants. In Tamil, there are only two cases where this forms conjuncts. More details in Section 3.3.2, “Virama/Pulli” of the [Proposal-Tamil].

Vowels and Matras: Separate symbols exist for all Vowels that are pronounced independently either at the beginning or after another vowel sound. To indicate a Vowel sound other than the implicit one following a consonant, a Vowel sign (matra) is attached to the consonant. Since the consonant has a built-in /a/, there are equivalent Matras for all vowels excepting the அ. More details in Section 3.3.3, “Vowels” in [Proposal-Tamil].

Visarga: The Visarga (or Aytham) is used in Tamil to represent a sound very close to /ḵ/. More details in Section 3.3.4, “Visarga/Aytham” in [Proposal-Tamil].

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

By default, the LGR includes the rules and actions to implement the following restrictions mandated by the IDNA protocol. They are marked with ⍟.

  • 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].

Default Actions

This LGR includes the 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].

Tamil-specific Rules and Action

These rules have been drafted to ensure that the prospective Tamil label conforms to akshar formation norms as desired in Tamil script. These norms are exclusively presented as context rules.

The following symbols are used in the WLE rules:
C → Consonant
M → Matra
H → Haleant / Virama =Pulli
X → Visarga = Aytham

The rules are:

  1. H: must be preceded by C
  2. M: must be preceded by C
  3. X: cannot be preceded by X

The following whole-label rule and associated action prevent the mixing of two allocatable variants of the same sequence within the same label. This reduces overproduction of variant labels.

  1. Two representations of ‘Shri’ cannot be mixed in the same label

More details in Section 7, “Whole Label Evaluation Rules (WLE)” in [Proposal-Tamil].

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 Tamil Script was developed by Michel Suignard and Asmus Freytag, based on the Root Zone LGR for the Tamil script and information contained or referenced therein; see [RZ-LGR-Taml]. 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 Tamil script, that this reference LGR is based on, was developed by the Neo-Brahmi Generation Panel (NBGP). For more information on methodology and contributors to the underlying Root Zone LGR, see Sections 4 and 8 in [Proposal-Tamil], as well as [RZ-LGR-Overview].

Changes from Version Dated 15 December 2020

Unicode Version has been updated.

Changes from Version Dated 24 January 2024

Adopted from the Second Level Reference LGR for the Tamil Script [Ref-LGR-und-Taml] 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),
Neo-Brahmi Generation Panel, “Proposal for a Tamil Script Root Zone Label Generation Rule-Set (LGR)”, 6 March 2019,
ICANN, Second Level Reference Label Generation Rules for the Tamil Script (und-Taml), 24 January 2024 (XML)
non-normative HTML presentation:
ICANN, Second Level Reference Label Generation Rules for the Tamil Script (und-Taml), 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 Tamil Script (und-Taml), 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 Tamil Script for the second level please see details in the Table of References below.

References [0] and [7] refer to the Unicode Standard versions in which the corresponding code points were initially encoded. References [101] and above correspond to sources given in [Proposal-Tamil] justifying the inclusion of 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 63
Number of code points
for each script
Tamil 48
Common 11
Number of code points 59
Number of sequences 4
Longest code point sequence 4

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    
U+0031 1 Common DIGIT ONE [0] Common-digit    
U+0032 2 Common DIGIT TWO [0] Common-digit    
U+0033 3 Common DIGIT THREE [0] Common-digit    
U+0034 4 Common DIGIT FOUR [0] Common-digit    
U+0035 5 Common DIGIT FIVE [0] Common-digit    
U+0036 6 Common DIGIT SIX [0] Common-digit    
U+0037 7 Common DIGIT SEVEN [0] Common-digit    
U+0038 8 Common DIGIT EIGHT [0] Common-digit    
U+0039 9 Common DIGIT NINE [0] Common-digit    
U+0B83 Tamil TAMIL SIGN VISARGA [0], [103] Visarga not: preceded-by-X   = aytham
U+0B85 Tamil TAMIL LETTER A [0], [101] Vowel      
U+0B86 Tamil TAMIL LETTER AA [0], [101] Vowel      
U+0B87 Tamil TAMIL LETTER I [0], [101] Vowel      
U+0B88 Tamil TAMIL LETTER II [0], [101] Vowel      
U+0B89 Tamil TAMIL LETTER U [0], [101] Vowel      
U+0B8A Tamil TAMIL LETTER UU [0], [101] Vowel      
U+0B8E Tamil TAMIL LETTER E [0], [101] Vowel      
U+0B8F Tamil TAMIL LETTER EE [0], [101] Vowel      
U+0B90 Tamil TAMIL LETTER AI [0], [101] Vowel      
U+0B92 Tamil TAMIL LETTER O [0], [101] Vowel      
U+0B92 U+0BB3 ஒள {Tamil} TAMIL LETTER O + TAMIL LETTER LLA   [Vowel] + [Consonant]   set 1 homoglyph of U+0B94
U+0B93 Tamil TAMIL LETTER OO [0], [101] Vowel      
U+0B94 Tamil TAMIL LETTER AU [0], [101] Vowel   set 1  
U+0B95 Tamil TAMIL LETTER KA [0], [102] Consonant      
U+0B99 Tamil TAMIL LETTER NGA [0], [102] Consonant      
U+0B9A Tamil TAMIL LETTER CA [0], [102] Consonant      
U+0B9C Tamil TAMIL LETTER JA [0], [102] Consonant      
U+0B9E Tamil TAMIL LETTER NYA [0], [102] Consonant      
U+0B9F Tamil TAMIL LETTER TTA [0], [102] Consonant      
U+0BA3 Tamil TAMIL LETTER NNA [0], [102] Consonant      
U+0BA4 Tamil TAMIL LETTER TA [0], [102] Consonant      
U+0BA8 Tamil TAMIL LETTER NA [0], [102] Consonant      
U+0BA9 Tamil TAMIL LETTER NNNA [0], [102] Consonant      
U+0BAA Tamil TAMIL LETTER PA [0], [102] Consonant      
U+0BAE Tamil TAMIL LETTER MA [0], [102] Consonant      
U+0BAF Tamil TAMIL LETTER YA [0], [102] Consonant      
U+0BB0 Tamil TAMIL LETTER RA [0], [102] Consonant      
U+0BB1 Tamil TAMIL LETTER RRA [0], [102] Consonant      
U+0BB2 Tamil TAMIL LETTER LA [0], [102] Consonant      
U+0BB3 Tamil TAMIL LETTER LLA [0], [102] Consonant      
U+0BB4 Tamil TAMIL LETTER LLLA [0], [102] Consonant      
U+0BB5 Tamil TAMIL LETTER VA [0], [102] Consonant      
U+0BB6 Tamil TAMIL LETTER SHA [7], [102] Consonant      
U+0BB6 U+0BCD U+0BB0 U+0BC0 ஶ்ரீ {Tamil} TAMIL SYLLABLE SHRII   [Consonant] + [Halant] + [Consonant] + [Matra]   set 2  
U+0BB7 Tamil TAMIL LETTER SSA [0], [102] Consonant      
U+0BB8 Tamil TAMIL LETTER SA [0], [102] Consonant      
U+0BB8 U+0BCD U+0BB0 U+0BC0 ஸ்ரீ {Tamil} TAMIL LETTER SA + TAMIL SIGN VIRAMA + TAMIL LETTER RA + TAMIL VOWEL SIGN II   [Consonant] + [Halant] + [Consonant] + [Matra]   set 2 Alternate for Tamil SHRII
U+0BB9 Tamil TAMIL LETTER HA [0], [102] Consonant      
U+0BBE  ா Tamil TAMIL VOWEL SIGN AA [0], [102] Matra follows-C    
U+0BBF  ி Tamil TAMIL VOWEL SIGN I [0], [102] Matra follows-C    
U+0BC0  ீ Tamil TAMIL VOWEL SIGN II [0], [102] Matra follows-C    
U+0BC1  ு Tamil TAMIL VOWEL SIGN U [0], [102] Matra follows-C    
U+0BC2  ூ Tamil TAMIL VOWEL SIGN UU [0], [102] Matra follows-C    
U+0BC6  ெ Tamil TAMIL VOWEL SIGN E [0], [102] Matra follows-C    
U+0BC6 U+0BB3  ெள {Tamil} TAMIL VOWEL SIGN E + TAMIL LETTER LLA   [Matra] + [Consonant] follows-C set 3 homoglyph of U+0BCC  ௌ 
U+0BC7  ே Tamil TAMIL VOWEL SIGN EE [0], [102] Matra follows-C    
U+0BC8  ை Tamil TAMIL VOWEL SIGN AI [0], [102] Matra follows-C    
U+0BCA  ொ Tamil TAMIL VOWEL SIGN O [0], [102] Matra follows-C    
U+0BCB  ோ Tamil TAMIL VOWEL SIGN OO [0], [102] Matra follows-C    
U+0BCC  ௌ Tamil TAMIL VOWEL SIGN AU [0], [102] Matra follows-C set 3  
U+0BCD  ் Tamil TAMIL SIGN VIRAMA [0], [102] Halant follows-C   = pulli


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 3
Largest variant set 2
Variants by Type
allocatable 2
blocked 4

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
0B92 0BB3 ஒள 0B94 blocked   Tamil homoglyph

Variant Set 2 — 2 Members

Source Glyph Target Glyph   Type Ref Comment
0BB6 0BCD 0BB0 0BC0 ஶ்ரீ 0BB8 0BCD 0BB0 0BC0 ஸ்ரீ allocatable   Alternate for Tamil SHRII

Variant Set 3 — 2 Members

Source Glyph Target Glyph   Type Ref Comment
0BC6 0BB3  ெள 0BCC  ௌ blocked   Tamil Homoglyph

Classes, Rules and Actions

Character Classes

Number of named classes 2
Implicit (except script) 4
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
C Tag=Consonant 23 {0B95 0B99-0B9A 0B9C 0B9E-0B9F 0BA3-0BA4 0BA8-0BAA 0BAE-0BB9}   Any Tamil consonant
X Tag=Visarga 1 {0B83}   The Tamil Visarga (aytham)
implicit Tag=Common-digit 10 {0030-0039}   Any character tagged as Common-digit
implicit Tag=Halant 1 {0BCD}   The character tagged as Halant
implicit Tag=Matra 11 {0BBE-0BC2 0BC6-0BC8 0BCA-0BCC}   Any character tagged as Matra
implicit Tag=Vowel 12 {0B85-0B8A 0B8E-0B90 0B92-0B94}   Any character tagged as Vowel
implicit Tag=sc:Taml 48 {0B83 0B85-0B8A 0B8E-0B90 0B92-0B95 0B99-0B9A 0B9C 0B9E-0B9F 0BA3-0BA4 0BA8-0BAA 0BAE-0BB9 0BBE-0BC2 0BC6-0BC8 0BCA-0BCD}   Any character tagged as Tamil
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 5
Used to trigger actions 2
Used as context rule (C) 3
Anchored context rules 3

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-C ([:C:])← ⚓︎   C   Section 7, WLE 1, 2: H and M must be preceded by C
preceded-by-X ([:X:])← ⚓︎   C   Section 7, WLE 3 , X cannot be preceded by X
no-mix-sri-shri (\u0BB6\u0BCD\u0BB0\u0BC0.*\u0BB8\u0BCD\u0BB0\u0BC0)|(\u0BB8\u0BCD\u0BB0\u0BC0.*\u0BB6\u0BCD\u0BB0\u0BC0)       Section 7: WLE 4: Two representations of ‘Shri’ cannot be mixed in the same 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.
( ) - 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).
⍟ - 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 no-mix-sri-shri invalid   do not mix two representations of ‘Shri’ in the same label
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: 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
[7] The Unicode Standard, Version 4.1
Any code point originally encoded in Unicode 4.1
[101] Omniglot, Tamil,
(Accessed on 21 Nov. 2017)
[102] Unicode 11.0.0, South and Central Asia-I, Page 488-493, R5 and R5a,
(Accessed on 5 July. 2018)
[103] Tamil Sign Visarga,
(Accessed on 27 Nov. 2017)
[150] RFC 5891, Internationalized Domain Names in Applications (IDNA): Protocol