the different between "使命" and " 任務" .i looked up dictionary and they are the same meaning "mission"
Both "使命 and "任務" mean an mission. The difference between them is the degree of difference.
"使命" is the mission nobody else but one can do, and one should become aware of its importance. On the other hand, "任務" is indeed not "task" but "mission". However, the importance of "任務" is less than that of "使命". Here are example sentences:
私の使命はこのチームを優勝に導くことだ。/ My mission is leading this team to victory.
私は上司が出した任務を終えた。/ I have accomplished the mission my boss ordered.
任務 refers to a relatively short-lived, concrete mission or order, like "protect the fortress" or "assassin someone". There is always a boss who gave it, and you typically need a few days or months to accomplish it.
使命 usually refers to a long-lived (or lifelong), general mission or vision of a person/organization. There doesn't have to be a boss, and it may be something given from God ("calling"). For example, "contribute to the human society using artificial intelligence", "propagate a religion alone in a distant country". So basically 使命 is a bigger word than 任務; a 使命 gives a meaning to your life.