く, in hiragana or ク in katakana, is one of the Japanese kana, which each represent one mora.

Both represent [kɯ] and their shapes come from the kanji 久.

This kana may have a dakuten added, transforming it into ぐ in hiragana, グ in katakana and gu in Hepburn romanization.

The dakuten's addition also changes the sound of the mora represented, to [ɡɯ] in initial positions and varying between [ŋɯ] and [ɣɯ] in the middle of words.

A handakuten (゜) does not occur with ku in normal Japanese text, but it may be used by linguists to indicate a nasal pronunciation [ŋɯ].