オツ

After a long day of work, you might say "お疲れ様" (otsukaresama) to a colleague. A shorter, more casual version is "___".

When acknowledging someone's effort in a very informal setting, you could use the shortened form of お疲れ様, which is "___".

Your friend just finished a tough study session. You want to give a quick, casual acknowledgement of their hard work. You could say "___".