A verb is a word (run) or a phrase (run out of) which expresses the existence of a state (love, seem) or the doing of an action (take, play). Two facts are basic:

Some grammarians believe that tense must always be shown by the actual form of the verb, and in many languages present, past and future are indicated by changes in the verb forms. On this reckoning, English really has just two tenses, the present and the past, since these are the only two cases where the form of the basic verb varies: love, write (present); loved, wrote (past).

However, it is usual (and convenient) to refer to all combinations of ''be + present participle'' and ''have + past participle'' as tenses. The same goes for ''will + bare infinitive'' to refer to the future (It will be fine tomorrow). But we must remember that tense in English is often only loosely related to time.

Tenses have two forms, simple and progressive (sometimes called 'continuous'). The progressive contains ''be + present participle'':

Simple forms and progressive combinations can also occur with:

• conditionals: I would work. I would be working.

• modals : I may work. I may be working.

Both simple and progressive forms usually give a general idea of when an action takes place. But the progressive forms also tell us that an activity is (or was, or will be, etc.) in progress, or thought of as being in progress.

This activity may be in progress at the moment of speaking:

• What are you doing? - I'm making a cake.

or not in progress at the moment of speaking:

• I'm learning to type. (i.e. but not at the moment of speaking)

Or the activity may be temporary or changeable:

• Fred was wearing a blue shirt yesterday.

Or the activity may be uncompleted:

• Vera has been trying to learn Chinese for years.

Our decision about which tense to use depends on the context and the impression we wish to convey.

Some verbs are not generally used in progressive forms. They are called stative because they refer to states (e.g. experiences, conditions) rather than to actions. In a sentence like:

• She loves/loved her baby more than anything in the world.

loves (or loved) describes a state over which the mother has no control: it is an involuntary feeling. We could not use the progressive forms (is/was loving) here.

Dynamic verbs, on the other hand, usually refer to actions which are deliberate or voluntary (I'm making a cake) or they refer to changing situations (He's growing old), that is, to activities, etc., which have a beginning and an end. Dynamic verbs can be used in progressive as well as simple forms. Compare the following:

progressive forms simple forms

1. Dynamic verbs with progressive and simple forms:

• I'm looking at you. I often look at you.

• I'm listening to music. I often listen to music.

2. Verbs which are nearly always stative (simple forms only):

•  I see you.

•  I hear music.

3. Verbs that have dynamic or stative uses:

deliberate actions states

• I'm weighing myself. I weigh 65 kilos.

• I'm tasting the soup. It tastes salty.

• I'm feeling the radiator. It feels hot.

Stative verbs usually occur in the simple form in all tenses. We can think of 'states' in categories like:

1 Feelings: like, love, etc.

2 Thinking/believing: think, understand, etc.

3 Wants and preferences: prefer, want, etc.

4 Perception and the senses: hear, see, etc.

5 Being/seeming/having/owning: appear, seem, belong, own, etc.

Sometimes verbs describing physical sensations can be used in simple or progressive forms with hardly any change of meaning:

• Ooh! It hurts! = Ooh! It's hurting.

Can/can't and could/couldn't often combine with verbs of perception to refer to a particular moment in the present or the past where a progressive form would be impossible:

• I can smell gas. = I smell gas.

Some adverbs like yesterday and tomorrow refer to past or future:

• I saw Jim yesterday. I'll be seeing Isabel tomorrow.

Other adverbs, such as already, always, ever, often, never, now, still can be used with a variety of tenses, though they may often be associated with particular ones. For example, always is often associated with the Simple Present or Past for habits:

• We always have breakfast at 7.30.

• Roland always took me out to dinner on my birthday.

But it can be used with other tenses as well:

• I shall always remember this holiday. (Future)

• Natasha has always been generous. (Present Perfect)

• Mr Biggs said he had always travelled first class. (Past Perfect)