中文譯英文

婚外情: has/have an affair / secret affair / extramarital affair

Affair: used to describe relationships outside our social conventions (社會不接納的關係)

Normally just the word AFFAIR would be enough to describe 婚外情, but if you want to make it sound more formal, you can use Extramarital Afair

http://www.fed.cuhk.edu.hk/~ceric/ajc/0401/0401101.htm

二奶: lover / mistress / ladylove / concubine

I suggest using LOVER or MISTRESS, which is more common nowadays and more people can understand.

婚外情 = Affairs
二奶 = Mistress

婚外情 = extra-marital affair.

二奶 = concubine

婚外情 ex-marital affair

婚外情:
His wife had many affairs, even, adding insult to injury, with his best friend.
他的太太有很多的婚外情,更糟的是跟他最好的朋友。
valentine
情人

2006-10-22 22:37:00 補充：
胡搞,婚外情All hell broke loose when his wife discovered he was fooling around with another woman.當他太太發現他跟別的女人胡搞時,情況變成一團混亂。

2006-10-22 22:40:36 補充：
妾 / 姘婦 / 姨太太 : concubine