cjk

CJK is an abbreviation for Chinese, Japanese, and Korean. In typography, publishing, and computing, the term groups these languages because they share a common heritage of Han characters and face similar challenges in character encoding, rendering, and font design. While the languages are distinct in grammar and pronunciation, their written forms involve Chinese-origin characters used across the three languages, with local scripts used alongside them.

Writing systems: Chinese uses Han characters as the core script, with regional variants and traditional and simplified forms. Japanese writes primarily with Kanji (Chinese characters) together with Kana syllabaries. Korean uses Hangul as the native script, though older texts and some specialized contexts employ Hanja (Chinese characters). The degree of character overlap among the languages varies, and each language has developed its own conventions for character usage and punctuation.

Computing and encoding: In modern computing, CJK text is encoded with Unicode, which includes the CJK Unified Ideographs blocks and various extensions. Before Unicode, region-specific encodings such as GB2312/GB18030 (Chinese), Big5 (Chinese), JIS X 0208 (Japanese), and KS C 5601 (Korean) were common. Han unification in Unicode groups matching Han characters across scripts into shared code points, but glyph shapes and usage differ by language, complicating font design and rendering.

Fonts and typography: CJK fonts must cover thousands of glyphs to render common text, including variants for simplification, traditional forms, and region-specific characters. Rendering involves balancing character set size, hinting, and metrics to ensure legibility at various sizes. In practice, “CJK” is used in typography, font packaging, and software localization to indicate support for these scripts.