Ru is one of the Japanese kana, each of which represent one mora. The hiragana is written in one stroke; the katakana in two. Both represent the sound. The Ainu language uses a small katakana ㇽ to represent a final r sound after an u sound. The combination of an R-column kana letter with handakuten ゜- る゚ in hiragana, and ル゚ in katakana was introduced to represent [lu] in the early 20th century.