Just as there are different kinds of noun, so there are different kinds of verb. The broad distinction is between lexical verbs and auxiliary verbs. This post considers the first of the two. Lexical verbs are those verbs that have traditionally been taught as ‘doing’ words. That’s fine as far as it goes, but a moment’s reflection shows the limitations of such an approach. What ‘actions’ do think, seem or exist describe? We could extend the definition by saying that verbs can describe a state or a condition as well as an action but, as with nouns, we need to consider the morphological and syntactical roles as well as the semantic one.
Most verbs come in different forms. Walk, as we have seen earlier, can occur as walk, walks, walking and walked. A word that can take all of those forms is undeniably a verb. Walk is a regular verb, but the verbs we use most tend to be irregular verbs, that is to say, we cannot predict their various forms without first learning them. There is an historical reason why sang and not singed is the past tense of sing and why drank and not drinked is the past tense of drink, but there is no rule that tells us that’s what it is.
We can also identify a word as a verb from the role it plays in a sentence. A typical sentence will often consist of a Noun Phrase (NP) and a Verb Phrase (VP). A NP has a noun as its head, that is, the main (and sometimes only) component. A VP is what is left and it has a verb as its head (and it, too, may be the only component). Within the VP we can recognize the verb by looking for a word that has the semantic and morphological features just described.
Finite and Non-finite
As with nouns, we can make further distinctions between verbs. Firstly, a verb can be finite or non-finite. Finite forms of the verb are those from which we can deduce answers to questions such as ‘Who?’ and ‘When?’ This means they are those forms that can show agreement with a preceding noun or pronoun, and which can tell us through their forms the time when whatever the verb is describing takes place.
Non-finite forms of the verb give no such indications. They comprise the –ing form, also known as the present participle or gerund; the form that in regular verbs ends in -d, known as the past participle; and the form traditionally known as the infinitive. The infinitive is also known as the base form and the plain form. It has often been thought of as including the particle to, but it does not invariably do so.
Tense and Aspect
When a verb tells us through its finite form when the event described takes place we can speak of its tense. If we think of tense as a change in the finite form of the verb in this way, then English has two tenses, present and past. He walks is present tense, he walked is past tense. The present tense of regular verbs such as walk has two forms, walk and walks. It has only one past tense from, walked. It contrasts with a verb like sing, which is irregular and native speakers as well as foreign learners have to learn its past tense sang, and its past participle sung as separate words.
Tense is closely related to aspect. Aspect describes the way in which the timing of the meaning expressed by the verb is viewed. I walked expresses perfective aspect, in which the event is viewed as an unanalysable whole. Often, it is expressed not through changes in the finite form of the verb, but through the use of the verb’s –ing form, or its past participle, in combination with forms of the the verb be and have. I am walking is an instance of the progressive aspect which typically indicates what the subject of the sentence is doing over a particular period of time. I have walked is an instance of the perfect aspect which typically describes a state resulting from an earlier event, and is usually relevant at the time of speaking. (Adapted from the article on Aspect in ‘Language and Linguistics: The Key Concepts’ by R L Trask.)