Variant form (Unicode)

A variant form is a different glyph for a character, encoded in Unicode through the mechanism of variation sequences: sequences in Unicode which consist of a base character followed by a variation selector character.

A variant form usually has a very similar appearance and meaning as its base form. The mechanism is intended for variant forms where, generally, if the variant form is unavailable, displaying the base character does not change the meaning of the text, and may not even be noticeable by many readers.

Unicode defines two types of variation sequences:^[1]

Standardized variation sequences defined in StandardizedVariants.txt^[1]^[2]
Ideographic variation sequences defined in the Ideographic Variation Database (IVD)^[3]^[4]

Variation selector characters reside in several Unicode blocks:

Variation Selectors (16 characters abbreviated VS1–VS16)
Variation Selectors Supplement (240 characters abbreviated VS17–VS256)
Mongolian (3 characters abbreviated FVS1–FVS3)

Variation selectors are not required for Arabic and Latin cursive characters, where substitution of glyphs can occur based on context: glyphs may be connected together depending on whether the character is the initial character in a word, the final character, a medial character or an isolated character. These types of glyph substitution are easily handled by the context of the character with no other authoring input involved. Authors may also use special-purpose characters such as joiners and non-joiners to force an alternate form of glyph where it would not otherwise appear. Ligatures are similar instances where glyphs may be substituted simply by turning ligatures on or off as a rich text attribute.

For other glyph substitution, the author's intent may need to be encoded with the text and cannot be determined contextually. This is the case with character/glyphs referred to as gaiji, where different glyphs are used for the same character either historically or for ideographs for family names. This is one of the gray areas in distinguishing between a glyph and a character: If a family name differs slightly from the ideograph character it derives from, then is that a simple glyph variant or a character variant?

Character substitutions may also occur outside of Unicode, for example with OpenType Layout tags.^[5]

Blocks with standardized variation sequences

As of Unicode 8.0, standardized variation sequences specifically for emoji/text presentation are defined for base characters in seventeen blocks:^[1]^[2]

Other standardized variation sequences are formed with base characters in the following eight blocks:^[1]^[2]

Blocks with ideographic variation sequences

As of 16 May 2014, ideographic variation sequences are defined for base characters in six blocks:^[3]^[4]

Variation Selectors block

Variation Selectors
Range	U+FE00..U+FE0F (16 code points)
Plane	BMP
Scripts	Common
Assigned	16 code points
Unused	0 reserved code points
Unicode version history

3.2	16 (+16)
Note: ^[6]

Variation Selectors is a Unicode block containing 16 Variation Selector format characters. They are used to specify a specific glyph variant for a Unicode character, such as the Japanese, Chinese, Korean, or Taiwanese form of a particular CJK ideograph.

They affect the glyph variant of the preceding character.

These combining characters are named variation selector-1 (for U+FE00) through to variation selector-16 (U+FE0F), and are abbreviated VS1 – VS16.

As of Unicode 8.0:^[1]^[2]

CJK compatibility ideograph variation sequences contain VS1–VS3 (U+FE00–U+FE02)
CJK Unified Ideographs Extension A and B variation sequences contain VS1 (U+FE00) and VS2 (U+FE01)
Emoji variation sequences contain VS16 (U+FE0F) for emoji-style or VS15 (U+FE0E) for text style
Manichaean, Phags-pa, and mathematical variation sequences contain only VS1 (U+FE00)
VS4–VS14 (U+FE03–U+FE0D) are not used for any variation sequences

Variation Selectors^[1] Official Unicode Consortium code chart (PDF)
	0	1	2	3	4	5	6	7	8	9	A	B	C	D	E	F
U+FE0x	VS 1	VS 2	VS 3	VS 4	VS 5	VS 6	VS 7	VS 8	VS 9	VS 10	VS 11	VS 12	VS 13	VS 14	VS 15	VS 16
Notes 1.^ As of Unicode version 8.0

Variation Selectors Supplement block

Variation Selectors Supplement
Range	U+E0100..U+E01EF (240 code points)
Plane	SSP
Scripts	Common
Assigned	240 code points
Unused	0 reserved code points
Unicode version history

4.0	240 (+240)
Note: ^[6]

Variation Selectors Supplement is a Unicode block containing additional Variation Selectors beyond those found in the Variation Selectors block.

These combining characters are named variation selector-17 (for U+E0100) through to variation selector-256 (U+E01EF), abbreviated VS17 – VS256.

As of 16 May 2014, VS17 (U+E0100) to VS48 (U+E011F) are used in ideographic variation sequences in the Unicode Ideographic Variation Database (IVD).^[3]^[4] However, as of Unicode 8.0, they are not found in any standardized variation sequence.

Variation Selectors Supplement^[1] Official Unicode Consortium code chart (PDF)
	0	1	2	3	4	5	6	7	8	9	A	B	C	D	E	F
U+E010x	VS 17	VS 18	VS 19	VS 20	VS 21	VS 22	VS 23	VS 24	VS 25	VS 26	VS 27	VS 28	VS 29	VS 30	VS 31	VS 32
U+E011x	VS 33	VS 34	VS 35	VS 36	VS 37	VS 38	VS 39	VS 40	VS 41	VS 42	VS 43	VS 44	VS 45	VS 46	VS 47	VS 48
U+E012x	VS 49	VS 50	VS 51	VS 52	VS 53	VS 54	VS 55	VS 56	VS 57	VS 58	VS 59	VS 60	VS 61	VS 62	VS 63	VS 64
U+E013x	VS 65	VS 66	VS 67	VS 68	VS 69	VS 70	VS 71	VS 72	VS 73	VS 74	VS 75	VS 76	VS 77	VS 78	VS 79	VS 80
U+E014x	VS 81	VS 82	VS 83	VS 84	VS 85	VS 86	VS 87	VS 88	VS 89	VS 90	VS 91	VS 92	VS 93	VS 94	VS 95	VS 96
U+E015x	VS 97	VS 98	VS 99	VS 100	VS 101	VS 102	VS 103	VS 104	VS 105	VS 106	VS 107	VS 108	VS 109	VS 110	VS 111	VS 112
U+E016x	VS 113	VS 114	VS 115	VS 116	VS 117	VS 118	VS 119	VS 120	VS 121	VS 122	VS 123	VS 124	VS 125	VS 126	VS 127	VS 128
U+E017x	VS 129	VS 130	VS 131	VS 132	VS 133	VS 134	VS 135	VS 136	VS 137	VS 138	VS 139	VS 140	VS 141	VS 142	VS 143	VS 144
U+E018x	VS 145	VS 146	VS 147	VS 148	VS 149	VS 150	VS 151	VS 152	VS 153	VS 154	VS 155	VS 156	VS 157	VS 158	VS 159	VS 160
U+E019x	VS 161	VS 162	VS 163	VS 164	VS 165	VS 166	VS 167	VS 168	VS 169	VS 170	VS 171	VS 172	VS 173	VS 174	VS 175	VS 176
U+E01Ax	VS 177	VS 178	VS 179	VS 180	VS 181	VS 182	VS 183	VS 184	VS 185	VS 186	VS 187	VS 188	VS 189	VS 190	VS 191	VS 192
U+E01Bx	VS 193	VS 194	VS 195	VS 196	VS 197	VS 198	VS 199	VS 200	VS 201	VS 202	VS 203	VS 204	VS 205	VS 206	VS 207	VS 208
U+E01Cx	VS 209	VS 210	VS 211	VS 212	VS 213	VS 214	VS 215	VS 216	VS 217	VS 218	VS 219	VS 220	VS 221	VS 222	VS 223	VS 224
U+E01Dx	VS 225	VS 226	VS 227	VS 228	VS 229	VS 230	VS 231	VS 232	VS 233	VS 234	VS 235	VS 236	VS 237	VS 238	VS 239	VS 240
U+E01Ex	VS 241	VS 242	VS 243	VS 244	VS 245	VS 246	VS 247	VS 248	VS 249	VS 250	VS 251	VS 252	VS 253	VS 254	VS 255	VS 256
Notes 1.^ As of Unicode version 8.0

Mongolian free variation selectors (FVS)

The Mongolian Unicode block contains its own variation selectors (listed as format controls) for use with the traditional Mongolian alphabet:^[7]

U+180B Mongolian free variation selector one (FVS1)
U+180C Mongolian free variation selector two (FVS2)
U+180D Mongolian free variation selector three (FVS3)

Additional variations may be also available for traditional Mongolian script characters according to the context of the character, or by using a zero-width joiner (ZWJ, U+200D) and/or a zero width non-joiner (ZWNJ, U+200C) to select the specific form. The block also contains format control named "Mongolian vowel separator" (MVS, U+180E).

References

1 2 3 4 5 "UCD: Standardized Variants". Unicode Consortium.
1 2 3 4 "UCD: Standardized Variation Sequences". Unicode Consortium.
1 2 3 "Ideographic Variation Database". Unicode Consortium.
1 2 3 "UTS #37, Unicode Ideographic Variation Database". Unicode Consortium.
↑ http://www.microsoft.com/typography/otspec/languagetags.htm
1 2 "Unicode Character Database (UCD)". The Unicode Standard. Retrieved 27 November 2015.
↑ http://www.unicode.org/versions/Unicode7.0.0/ch13.pdf#G27882

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