In CJK (Chinese, Japanese, and Korean) computing, graphic characters are traditionally classed into fullwidth and halfwidth characters. Unlike monospaced fonts, a halfwidth character occupies half the width of a fullwidth character, hence the name.
Halfwidth and Fullwidth Forms is also the name of a Unicode block U+FF00–FFEF, provided so that older encodings containing both halfwidth and fullwidth characters can have lossless translation to and from Unicode.