Katsudō (活動) refers to 'activity' or 'action.' It often describes organized actions performed as part of a group, club, or for a specific purpose, such as volunteer work or school clubs. For example, '彼はボランティア活動をしています' (He is doing volunteer activities).

何か目的を持って行う「行動」や「動き」のことです。例：クラブ活動をします。