theory

n.

1. 学说
   • There are many theories about the origin of life.
     关于生命起源的学说有很多。
2. 理论, 原理
   • Your plan sounds fine in theory.
     你的计划在理论上听起来不错。
3. 意见, 看法
   • She has a theory that drinking milk prevents colds.
     她有一种说法, 认为喝牛奶能防止感冒。