Osu

Osu (押忍, often written oss) is the all-purpose verbal acknowledgement in a karate dojo — the equivalent of "yes", "understood", "thank you", and "I'll push through" rolled into one short syllable.

Students say it when greeted, when given an instruction, when bowing in rei, and when finishing a drill. It carries a spirit of pushing past discomfort — the kanji roughly combine "push" and "endure". Use varies by style: very common in Shotokan and Kyokushin, while some traditional schools use it more sparingly.