beholder

名词 beholder:

1. a person who becomes aware (of things or events) through the senses
   同义词：perceiver, percipient, observer

1. I don't understand how he can think she is good looking, but beauty is in the eye of the beholder.
   我不明白他怎么会认为她漂亮，不过情人眼里出西施罢了。
2. She seems very plain but he dotes on her, but beauty is in the eye of the beholder.
   她看上去相貌平平，但他非常爱她，情人眼中出西施。