Using the instead of my in "the wife" does subtly change the meaning of a sentence it's used in.
Assuming the woman in question is the wife of the speaker, compare
It's my wife on the phone.
to
It's the wife on the phone.
Using the instead of my puts a bit of social distance between the speaker and their wife. Even if the listener knows that the speaker is talking to the speaker's wife, the use of the decouples the couple.
Using the wife when talking about someone else's wife is possible, but is different in meaning. In this context you can use the wife to mean his wife, her wife, their wife or their wives, i.e. it can only apply to a third person pronoun.
Imagine A is on the phone and B wants to know who A is talking to:
B: Are you talking to the husband?
A: No, it's the wife.
So A is talking to the wife of the couple they are interested in.
The wife would not work if someone's name was used:
B: Are you talking to Mr. Jenkins?
A: No, it's the wife.
Here the wife would be taken to mean A's wife, rather than Mr. Jenkin's wife, although it is possible that there might be confusion as to what A means.
As Barrie England points out, you can also use the wife to mean your wife as in "How is the wife." I agree with him that this is only something that would be done if you are sure your remark won't be taken as an insult.
Other constructs that are similar:
- Female
- The wife (fiancée, girlfriend)
- The old lady (and other such euphemisms for wife, "the ball and chain", etc.)
- The mother in law
- Male
- The husband (fiance, boyfriend)
- The old man (and other such euphemisms for husband)
- The father in law
The pattern is that someone uses the in place of my when they are married to or related by marriage to someone and don't like, or are pretending not to like, the person in question.
Best Answer
Use I when you are the subject and use me when you are the object.
You may remember a simple rule that will work most of the time.
Remove all the rest and see if the sentence still makes sense.