expression as bound or length

例句：

1. 1. The artist's expression on the canvas is captivating.
   艺术家在画布上的表情令人着迷。
2. 2. She gave a warm smile to express her gratitude.
   她用温暖的微笑来表达她的感激之情。
3. 3. His words were meant to express his feelings of sadness.
   他的话是想要表达他的悲伤情感。