The term anomalous finites is used to refer to the group of 24 finites given below:

Present Tense: Is, am, are, has, have, do, does, shall, will, can, may, must, ought, need and dare
Past tense: was, were, had, did, should, would, could, might, used

You will have noticed that these are all auxiliaries. Some of them are also used as main verbs. As auxiliaries they help main verbs to form their tenses and moods. As anomalous finites they serve other purposes.

Note that anomalous finites are irregular verbs because they do not form the past tense in the regular manner by the addition of –ed, -d or –t, but by a change in the root vowel. Some anomalous finites such as must, ought, need and dare have no past tense forms at all.

These irregular verbs, however, are different from other irregular verbs in their function and hence are called anomalous finites or special finites.

One of the major differences is that unlike other finites, anomalous finites can be used along with n’t, the shortened form of not.

It isn’t true. (= It is not true.)
We aren’t coming. (= We are not coming)
You shouldn’t wait. (= You should not wait.)

Here is a list of the contracted forms of the anomalous finites + not. The uncontracted form is given in the brackets.

Ain’t (I’m not – colloquial)
Isn’t (is not), aren’t (are not), wasn’t (was not), weren’t (were not), haven’t (have not), hasn’t (has not), hadn’t (had not), don’t (do not), doesn’t (does not), didn’t (did not), shan’t (shall not), shouldn’t (should not), won’t (will not), wouldn’t (would not), can’t (cannot), couldn’t (could not), mayn’t (may not), mightn’t (might not), mustn’t (must not), oughtn’t (ought not), needn’t (need not), daren’t (dare not)

Read the sentence given below:

I haven’t posted the letter.

Here have is an auxiliary verb because it helps to form the present perfect of post. It is also anomalous because it combines with n’t.

The use of anomalous finites

To make negative sentences

In modern English, you can’t make a negative sentence by simply adding not to the positive sentence. In fact, only the anomalous finites can form their negatives by the simple addition of not.