け, in hiragana, or ケ in katakana, is one of the Japanese kana, each of which represents one mora. Both represent [ke]. The shape of these kana come from the kanji 計 and 介, respectively.
A dakuten may be added to this character; this changes it to げ in hiragana, ゲ in katakana, ge in Hepburn romanization, and the pronunciation shifts to [ɡe] in initial positions, and varying between [ŋe] and [ɣe] in the middle of words.
A handakuten (゜) does not occur with ke in normal Japanese text, but it may be used by linguists to indicate a nasal pronunciation [ŋe].