Most English verbs can occur in either the simple form or the progressive form. This section discusses the general differences in form, use, and meaning between the simple form and the progressive form.
The simple form
If a verb phrase is not in the progressive form (and not in the perfect) it is said to have simple form. In this section only verb phrases consisting of a main verb alone are referred to as simple, although the term 'simple verb phrase' may refer to more complex verb phrases than this.
The progressive form
The progressive form of an English verb phrase consists of a form of the verb be followed by the present participle (the -ing form) of another verb. In the simplest case, a verb phrase in the progressive consists of two verbs only:
(1) Bill is singing.
However, both the first part of the progressive, i.e. the verb BE (the capital letters indicate that we are talking about a form of the verb be), and the second part, i.e. the -ing form, may be part of another combination of verbs in the verb phrase. Thus, the first part of the progressive form may also be the second part of the perfect (enclosed in square brackets in the following example):
(2) Bill [has been] singing.
Conversely, the second part of the progressive may be the first part of the passive (enclosed in square brackets in the following example):
(3) A new song was [being sung] throughout the city.
Contrasting simple and progressive verb phrases.
The simple and progressive forms contrast in several different ways. The most important one is illustrated in the following examples.
(1a) It is raining a lot in London
(1b) It rains a lot in London.
In the first sentence, the speaker is making a claim about what the weather conditions are like in London at the time the utterance is made. This use is sometimes referred to as the present continuous, to reflect the fact that some event is ongoing at a particular point in time. The second sentence makes a claim about what the weather is normally like in London, but crucially makes no claim about what the weather is like at the time of utterance. A similar contrast is found in the following pair of examples:
(2a) Bill is playing tennis.
(2b) Bill plays tennis.
Again, the progressive form indicates that the event is ongoing at the time of utterance, whereas the simple form describes a habit of Bill's. Thus, although it is claimed that he is a habitual tennis player, no claim is made about whether or not he is playing right now.
In the past tense, the progressive indicates that an event, etc. was ongoing at a particular time or during a period in the past.
(3) It was raining this morning.
The time in the past at which the event was ongoing can itself be presented as an event.
(4) It was raining when Bill left for work.
Sometimes, another event may interrupt the ongoing event.
(5) Bill was walking down the street when a woman stopped him.
Since stative verbs denote stable states of affairs, many of them do not easily occur in the progressive form. For example, verbs denoting ownership in a wide sense do not occur in the progressive.
(6) In many countries the government owns the railways. (Not: *is owning)
(7) The Vice-Chancellor has a small personal secretariat which also oversees directly the central press and public relations activity of the University. (Not: *is having)
(8) Many economists argue that a commodity possesses several useful characteristics, only one of which is its price. (Not: *is possessing)
Similarly, verbs denoting mental states and attitudes only very rarely occur in the progressive.
(9) The students appreciated Professor Smith's sense of humour.
(10) Physicists know as much about the nucleus now as Bohr did about the atom in 1920.
(11) If there is enough evidence, the researcher rejects the null hypothesis and concludes that medication has an effect on the patient.