I'm currently learning some vocab through wanikani, and they have these two words 仕草 and 作用 both meaning "action", but no nuance is explained, and when checking on jishou for a more proper word for action that could fit everywhere, and found three more to add to the list. So could anyone shed some light on the different usages of these words please ?
活動 is a habitual activity, eg hobby, routine, club activities, or even limited-time sustained effort (eg 就職活動 = job hunt)
行動 is a more generic one-shot behavior or action
仕草 is more about the way you carry yourself, mannerisms, motions, etc.
作用 ~ not much experience with this one, but I believe it is a process, eg a scientific or biological process.