"mistress" in Chinese (Simplified)
情妇女主人女教师
Definition
“Mistress” 可以指与已婚男子有恋爱或性关系的女人。在较旧或正式的用法中，它也可以指有权威地位的女性，比如一家之主或女教师。
Usage Notes (Chinese (Simplified))
现在最常见的意思是“已婚男人的情妇”，通常带有负面或八卦色彩。较旧的意思多见于固定表达如 “schoolmistress” 或历史语境中；“master and mistress of the house” 很正式，也比较过时。
Examples
The king kept a mistress in secret.
国王秘密地养了一位**情妇**。
In the old story, she was the mistress of a large house.
在那个古老的故事里，她是一座大宅的**女主人**。
The children listened to their mistress at school.
孩子们在学校听他们的**女教师**的话。
He left his wife and moved in with his mistress.
他离开了妻子，搬去和**情妇**同住了。
In that period drama, the mistress of the estate controls everything.
在那部年代剧里，庄园的**女主人**掌控着一切。
The term mistress sounds old-fashioned unless you mean a lover.
“**mistress**” 这个词听起来很过时，除非你指的是情人。