Katakana is one of the two Japanese phonetic writing systems, consisting of 46 basic characters. It was derived from parts of Chinese characters and features angular, straight-lined shapes.

Katakana is primarily used for foreign loanwords (コンピュータ for "computer"), onomatopoeia, scientific terms, and emphasis. Japanese writing system books explain when to use katakana vs hiragana.

In Unicode, full-width katakana occupies U+30A0 to U+30FF, while half-width katakana is at U+FF65 to U+FF9F. Half-width katakana is rarely used in modern systems but remains for legacy compatibility.

For character counting, both full-width and half-width katakana count as one character each. Japanese language references cover katakana usage rules in detail.