Envelops
n. 包络线；信封（envelop的复数）
🗣️ 情景例句
The front wheels are out of alignment.
前轮不平行了。
All things are difficult before they are easy.
凡事必先难后易。
It was difficult not to be tempted.
要想不为这些东西所动心是很困难的。