mean standard deviation

例句：

1. 1. He means to go for a walk after dinner.
   他打算晚饭后去散步。
2. 2. The meaning of life is to live it fully.
   生活的意义在于充分地生活。
3. 3. The teacher meant to be sympathetic, but he was too busy.
   老师本意是表示同情，但他太忙了。