The Penn Treebank Parts of Speech tag set differentiated between the base form of verbs (VB), and the non-3rd person singular present form (VBP).

Consider the following cases, with the different uses of rise:

base form: The share price will rise.

non-3rd person singular present: The share prices rise.

In both cases the forms are the same.

All the examples I have seen of verbs where that is not true, are with verbs that can be considered (by some definition) to be modal and/or auxiliary. Such as: be, am, are, is, was, were, being, can, could, do, did, does, doing, have, had, has, having, may, might, must, shall, should, will, or would

Are there examples of words from outside my modal/auxiliary list, of non-3rd person singular present forms that are different from their base forms?

I would particularly appreciate referenced answers, sourcing any statements about their nonexistence/rarity.

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    This is not a suitable question for ELU; my adding 'it is best not to regard be, have, and do as auxiliaries in some usages' may confuse a learner. Certainly the verb will as in 'she willed her paintings to charity' is not an auxiliary. Jul 22, 2015 at 9:30
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    @EdwinAshworth Neither is willed a modal verb in that example.
    – Andrew Leach
    Jul 22, 2015 at 9:32
  • @Andrew Leach Really necessary? '... the modal auxiliaries are can, could, may, might, must, shall, should, will, and would.' (ODO) Jul 22, 2015 at 9:37
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    @EdwinAshworth what do you mean by "not a suitable question [as] ... may confuse a learner?". surely advanced topics/confusing topics are definitely ontopic here? (But not on ELL perhaps, which is for learners) Jul 22, 2015 at 9:37
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    Sorry I don't get why can, have, do etc are exceptions? The only exception here is BE. The only reason to say that a modal such as can is different is perhaps just because they cannot be proven to have a base form. Jul 22, 2015 at 10:14

2 Answers 2


The answer to the OP's question is: 'yes'. Mostly. The only English verb which differs from its plain form outside of the third person, is the verb BE. The verb BE is usually an auxiliary verb.

However, the verb BE can also be regarded as a lexical verb in sentences such as:

  • If you don't be careful ...

Notice that the sentence above uses DO as a dummy auxiliary even though BE is present. Because of this there might possibly be cases where it is impossible to distinguish between BE as a lexical or auxiliary verb. However, I know of no such cases. Lexical BE rarely if ever rears it's head as a tensed verb. Arguably the positive polarity version of the phrase above is:

  • If you be careful

Here we are still using the plain form of the verb, not the present tense. There is a strong case therefore that tensed BE is always an auxiliary. This would mean that there are no exceptions to this rule.

However, there is one more issue that might put a spanner in the works here. The verbs BEWARE and USED have no present tense form in current usage. BEWARE is only ever used in the plain form because it only occurs in imperative constructions. The verb USED as in I used to smoke, is only used in the past tense. It could be argued, therefore, that these verbs do not have any present tense form that is identical to the base or plain form.

You can read more about lexical versus auxiliary BE in the reference grammar The Cambridge Grammar of the English Language by Huddleston & Pullum, 2002.

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    For the reference of others, the key statement: "...verbs other than be this form [non-3rd person singular present tense] is synchronized with the plain form." is on page 84, first paragraph under heading 1.6, of The Cambridge Grammar of the English Language by Huddleston & Pullum, 2002. Jul 23, 2015 at 5:08

Your list is a bit lop-sided as modal verbs have no infinitive, only one form for present tense and one form for past tense, with the exception of must, that normally is not used in past tense. And it is wrong to include to have and to do. These verbs have the same form for the infinitive and for present tense (to have/I have, to do/I do).

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