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

Not to be confused with sokuon, which are identical but somewhat smaller.

Also note that, as in the other -u kana, the 'u' sound is very subtle; unless well-articulated, this kana sounds fairly close to 'ts' alone.

Kana

つ | つ | つ | つ