English grammar - Roger Berry 2012

A5.2 Finite forms vs non-finite forms
A5 Verbs and their forms
Section A. Introduction

We make one basic distinction between verb forms: between ’finite’ (or ’tensed’) forms and ’non-finite’ (or ’non-tensed’) forms. The three finite forms are the present, third person singular -s and past tense forms; they are the ones to do with tense.

The three non-finite forms are the infinitive, and -ing and -ed participles. (There are four if we distinguish the bare infinitive from the to infinitive, e.g. love and to love.) The reason for distinguishing them is that non-finite forms cannot make a verb phrase on their own (see A6); they are ’unfinished’ and need a finite form to complete them. Finite (complete) forms, by contrast, may stand on their own. Since tense is an obligatory choice in English, all verb phrases must be either present or past.

So, although the present and infinitive have the same form (except in the case of be), it is important to distinguish them. For example, the two following sentences seem to be identical apart from the addition of will:

a) I have it

b) I will have it

But in fact what is really happening is that one finite form in a), the present tense have, is being replaced by another, will, in b), and it is the non-finite infinitive, have, in b) that is being added. See C5 for another example of this.

This distinction will be important when we discuss verb phrases in A6 and clauses in later sections.