太太: used for introducing the wife in a business party (Most frequently used) 老婆: when people meet their friends and buddies (Most frequently used) 内人: Normally we won't use it. It is kindof traditional way of saying Wife. 妻子: It is less popular than 老婆 but more popular than 内人.

with close friends and relative, we use “老婆”， with colleagues we use “爱人”， “妻子”is usually used in literature, “太太”is mostly formally used in business occasion.

Hi! I think "taitai" is more polite form of "qizi". I believe that it used to be that a man referred to his own wife as "qizi" and someone else's wife as "taitai" (to be more polite). But I have noticed that a man can also refer to his own wife as "taitai" now. My Chinese is not so good, but that's what I thought.

太太tai tai,老婆lao po,妻子qi zi,爱人ai ren

to plus MS help's answer with hada's and in add to their answers i will give you another examples for wife if i am with my wife to go to a party and then i will introduce my wife to my friends like " 这是我爱人"（这是更为正式的一种说法more formal 她——我老婆。 in a kidding way if i write a letter to my wife i would write 我最深爱的妻子(my beloved wife）