When you ask an affirmative question at the end of a sentence, you are supposed to use the contracted version of a verb. For example:
- You have done your homework already, haven’t you?
- He is from England, isn’t he?
- You went on a holiday last week, didn’t you?
There is no problem with contracted forms of “have” and “do”. However, what if you were to say, “I am new here, …n’t I?” What would the three dots stand for?
Unless you are in Scotland, people will find it funny if you say “amn’t I”. Since there is no other way to contract “am not”, this, theoretically, leaves you with only one possibility:
However, if you use the full negative form of a verb (as in the previous example), it puts strong, often even authoritative emphasis on the preceding statement. For example, a teacher arguing with a disrespectful pupil could say “I believe I am your teacher, am I not?”
Because of this authoritative connotation, another way of saying “am I not” developed. Virtually all native speakers now use the form “aren’t I”, which is now completely acceptable in any spoken or informal written context. To sum it up: