CJK Unified Ideographs
Encoding for shared Han characters
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Through Writing system and Character encoding
The term ideographs is a misnomer, as the Chinese script is not ideographic but rather logographic, but was chosen for being more common in English.
Until the early 20th century, Vietnam also used Chinese characters (Chữ Nôm), so sometimes the abbreviation CJKV is used.
Ordering
The ordering of CJK Unified Ideographs within Unicode blocks (not counting those added to the block later) was initially determined by consulting the following four dictionaries. Primarily, they were arranged in Kangxi Dictionary order, with the other dictionaries consulted, in order, for characters not found in the Kangxi Dictionary, to determine which Kangxi Dictionary character they should follow in the ordering.
- Kangxi Dictionary
- Dai Kan-Wa Jiten
- Hanyu Da Zidian
- Dae Jaweon
This system is not used for more recently-added Unicode blocks. The Ideographic Research Group no longer uses the Dae Jaweon, nor the Dai Kan-Wa Jiten, in its work. The Kangxi Dictionary and Hanyu Da Zidian are still used both in existing character source references, and as potential replacements for existing source references discovered to be erroneous. Similarly, although a (real or virtual) Kangxi Dictionary index was previously provided as part of the submission data for UTC-source characters, this is no longer the case. Instead, the stroke type of the first residual stroke (first stroke which does not form part of the radical) is supplied with all submitted characters, and used to order characters with the same radical and stroke count within the new Unicode block.
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CJK Unified Ideographs blocks
CJK Unified Ideographs
The basic block named CJK Unified Ideographs (4E00–9FFF) contains 20,992 basic Chinese characters in the range U+4E00 through U+9FFF. The block not only includes characters used in the Chinese writing system but also kanji used in the Japanese writing system, hanja in Korea, and chữ Nôm characters in Vietnamese. Many characters in this block are used in all three writing systems, while others are in only one or two of the three.
This block is also known as the Unified Repertoire and Ordering (URO), especially when it needs to be differentiated from the other CJK Unified Ideographs blocks.
The first 20,902 characters in the block are arranged according to the Kangxi Dictionary ordering of radicals. In this system the characters written with the fewest strokes are listed first. The remaining characters were added later, and so are not in radical order.
The block is the result of Han unification, which was somewhat controversial within East Asia. Since single characters used in more than one of Chinese, Japanese and Korean were coded in the same location, and the modern typographical conventions and handwriting curricula differ slightly between regions (not necessarily along language boundaries—for example, Hong Kong and Taiwan, which both use Traditional Chinese, have slightly different local conventions), the appearance of a selected glyph could depend on the particular font being used. However, the URO applies the source separation rule, meaning that pairs of characters treated as distinct in a character set used as a source for the URO (e.g. JIS X 0208 as used in e.g. Shift JIS) would remain pairs of separate characters in the new Unicode encoding.
Using variation selectors, it is possible to specify certain variant CJK ideograms within Unicode. The Adobe-Japan1 character set, which has 14,684 ideographic variation sequences, is an extreme example of the use of variation selectors.
Charts
4E00–62FF, 6300–77FF, 7800–8CFF, 8D00–9FFF.
CJK Unified Ideographs Extension A
The block named CJK Unified Ideographs Extension A (3400–4DBF) contains 6,592 additional characters in the range U+3400 through U+4DBF.
Charts
3400–4DBF.
CJK Unified Ideographs Extension B
The block named CJK Unified Ideographs Extension B (20000–2A6DF) contains 42,720 characters in the range U+20000 through U+2A6DF. These include most of the characters used in the Kangxi Dictionary that are not in the basic CJK Unified Ideographs block, as well as many Hán-Nôm characters that were formerly used to write Vietnamese.
Charts
20000–215FF, 21600–230FF, 23100–245FF, 24600–260FF, 26100–275FF, 27600–290FF, 29100–2A6DF.
CJK Unified Ideographs Extension C
The block named CJK Unified Ideographs Extension C (2A700–2B73F) contains 4,160 characters in the range U+2A700 through U+2B73F. It was initially added in Unicode 5.2 (2009).
Charts
2A700–2B73F.
CJK Unified Ideographs Extension D
The block named CJK Unified Ideographs Extension D (2B740–2B81F) contains 223 characters in the range U+2B740 through U+2B81E. It was originally added in Unicode 6.0 (2010).
Charts
2B740–2B81F.
CJK Unified Ideographs Extension E
The block named CJK Unified Ideographs Extension E (2B820–2CEAF) contains 5,774 characters in the range U+2B820 through U+2CEAD. It was originally added in Unicode 8.0 (2015).
Charts
2B820–2CEAF.
CJK Unified Ideographs Extension F
The block named CJK Unified Ideographs Extension F (2CEB0–2EBEF) contains 7,473 characters in the range U+2CEB0 through 2EBE0 that were added in Unicode 10.0 (2017). It includes more than 1,000 Sawndip characters for Zhuang.
Charts
2CEB0–2EBEF.
CJK Unified Ideographs Extension G
A block named CJK Unified Ideographs Extension G was added as part of Unicode 13.0 to the Tertiary Ideographic Plane in the range U+30000 through U+3134F, containing 4,939 characters.
Charts
30000–3134F.
CJK Unified Ideographs Extension H
A block named CJK Unified Ideographs Extension H was added as part of Unicode 15.0 to the Tertiary Ideographic Plane in the range U+31350 through U+323AF, containing 4,192 characters.
Charts
31350–323AF.
CJK Unified Ideographs Extension I
A block named CJK Unified Ideographs Extension I was added as part of Unicode 15.1 to the Supplementary Ideographic Plane in the range U+2EBF0 through U+2EE5F, containing 622 characters.
Charts
2EBF0–2EE5F.
CJK Unified Ideographs Extension J
A block named CJK Unified Ideographs Extension J was added as part of Unicode 17.0 to the Tertiary Ideographic Plane in the range U+323B0-U+3347F, containing 4,298 characters.
Charts
323B0–3347F.
CJK Compatibility Ideographs
The block named CJK Compatibility Ideographs (F900–FAFF) was created to retain round-trip compatibility with other standards.
However, twelve characters in this block actually have the "Unified Ideograph" property: U+FA0E 﨎, U+FA0F 﨏, U+FA11 﨑, U+FA13 﨓, U+FA14 﨔, U+FA1F 﨟, U+FA21 﨡, U+FA23 﨣, U+FA24 﨤, U+FA27 﨧, U+FA28 﨨, and U+FA29 﨩. None of the other characters in this and other "Compatibility" blocks relate to CJK unification.
While 龜 and 亀 are not considered unifiable, U+FA20 蘒 CJK COMPATIBILITY IDEOGRAPH-FA20 is considered a duplicate to U+8612 蘒 CJK UNIFIED IDEOGRAPH-8612.
Charts
F900–FAFF.
Known issues
Disunification
U+4039
The character U+4039 (䀹) was a unification of two different characters (one with jiā 夾 phonetic and one with shǎn 㚒 phonetic) until Unicode 5.0. However, they were lexically different characters that should not have been unified; they have different pronunciations and different meanings.
The proposal of disunification of U+4039 was accepted for Unicode 5.1, encoding a new character at U+9FC3 (鿃) to represent shǎn.
Other 3 glyphs in Extension B
In CJK Unified Ideographs Extension B, some characters were incorrectly unified with others. These characters include U+2017B (𠅻), U+204AF (𠒯) and U+24CB2 (𤲲). The first two characters contained a wrong unification of Chinese and Vietnamese source of their glyph, while the last one unifies the Chinese and Taiwanese ones.
The glyphs for U+2017B (𠅻) and U+204AF (𠒯) were corrected in version 10.0, and the erroneous UCS2003 source glyph U+24CB2 (𤲲) was removed in version 13.0.
Unifiable variants and exact duplicates
Also in CJK Unified Ideographs Extension B, hundreds of glyph variants were encoded by mistake. Additionally, an ISO/IEC JTC 1/SC 2 report has found that six exact duplicates (where the same character has inadvertently been encoded twice) and two semi-duplicates (where the CJK-B character represents a de facto disunification of two glyph forms unified in the corresponding BMP character) were encoded by mistake:
- U+34A8 㒨 = U+20457 𠑗 : U+20457 is the same as the China-source glyph for U+34A8, but it is significantly different from the Taiwan-source glyph for U+34A8
- U+3DB7 㶷 = U+2420E 𤈎 : same glyph shapes
- U+8641 虁 = U+27144 𧅄 : U+27144 is the same as the Korean-source glyph for U+8641, but it is significantly different from the mainland China-, Taiwan- and Japan-source glyphs for U+8641
- U+204F2 𠓲 = U+23515 𣔕 : same glyph shapes, but ordered under different radicals
- U+249BC 𤦼 = U+249E9 𤧩 : same glyph shapes
- U+24BD2 𤯒 = U+2A415 𪐕 : same glyph shapes, but ordered under different radicals
- U+26842 𦡂 = U+26866 𦡦 : same glyph shapes
- U+FA23 﨣 = U+27EAF 𧺯 : same glyph shapes (U+FA23 﨣 is a unified CJK ideograph, despite its name "CJK COMPATIBILITY IDEOGRAPH-FA23.")
Other CJK ideographs in Unicode, not Unified
Apart from the eleven blocks of "Unified Ideographs," Unicode has about a dozen more blocks with not-unified CJK-characters. These are mainly CJK radicals, strokes, punctuation, marks, symbols and compatibility characters. Although some characters have their (decomposable) counterparts in other blocks, the usages can be different. An example of a not-unified CJK-character is U+3007 〇 IDEOGRAPHIC NUMBER ZERO in the CJK Symbols and Punctuation block. Although it is not covered under "CJK Unified Ideographs", it is treated as a CJK-character for all other intents and purposes.
Four blocks of compatibility characters are included for compatibility with legacy text handling systems and older character sets:
- CJK Compatibility (3300–33FF)
- CJK Compatibility Forms (FE30–FE4F)
- CJK Compatibility Ideographs (F900–FAFF)
- CJK Compatibility Ideographs Supplement (2F800–2FA1F)
They include forms of characters for vertical text layout and rich text characters that Unicode recommends handling through other means. Therefore, their use is discouraged.
Unihan database
The Unihan database maintained by the Unicode Consortium provides information about all of the unified Han characters encoded in the Unicode Standard, including mappings to various national and industry standards, indices into standard dictionaries, encoded variants, pronunciations in various languages, and an English definition. The database is available to the public as text files and via an interactive website. The latter also includes representative glyphs and definitions for compound words drawn from the free Japanese EDICT and Chinese CEDICT dictionary projects (which are provided for convenience and are not a formal part of the Unicode Standard).
Font support
The blocks CJK Unified Ideographs and CJK Unified Ideographs Extension A, being parts of the Basic Multilingual Plane, are supported by the majority of the CJK fonts. However, Japanese and Korean fonts usually have fewer characters (about 13,000 and 8,000, respectively) than Chinese. Extensions B, C, D are supported by additional fonts MingLiU-ExtB, MingLiU_HKSCS-ExtB, PMingLiU-ExtB, SimSun-ExtB included in Microsoft Windows since Vista.