The progressive forms of a verb indicate that something is happening or was happening or will be happening. When used with the past, the progressive form shows the limited duration of an event: "While I was doing my homework, my brother came into my room." The past progressive also suggests that an action in the past was not entirely finished. (Compare "I did my homework." to "I was doing my homework.") This is even more evident in the passive progressive construction: "He was being strangled in the alley" suggests an action that was not finished, perhaps because the act was interrupted by a good citizen, whereas the simple past "He was strangled in the alley" suggests an action that was finished, unfortunately.
A neat categorization of the uses of the progressive can be found on the page describing the "To Be" Verb.
The progressive forms occur only with dynamic verbs, that is, with verbs that show qualities capable of change as opposed to stative verbs, which show qualities not capable of change.* For instance, we do not say, "He is being tall" or "He is resembling his mother" or "I am wanting spaghetti for dinner" or "It is belonging to me." (We would say, instead: "He is tall," "He resembles his mother," "I want spaghetti," and "It belongs to me.") The best way to understand the difference between stative and dynamic verbs is to look at a table that lists them and breaks them into categories and then to build some sentences with them, trying out the progressive forms to see if they work or not.
These categories and lists are derived from Randolph Quirk and Sidney Greenbaum's A University Grammar of English (used with the publisher's permission). The examples are our own. The lists are not meant to be complete.
DYNAMIC VERBS | |||
Activity Verbs I am begging you. I was learning French. They will be playing upstairs.. Virtually identical in meaning to simple tense forms: I beg you. I learned French. They will play upstairs. | |||
abandon ask beg call drink | eat help learn listen look at |
play rain read say slice |
throw whisper work write |
Process Verbs The corn is growing rapidly. Traffic is slowing down. Virtually identical in meaning to simple present tense forms: The corn grows rapidly. Traffic slows down. | |||
change deteriorate | grow mature | slow down | widen |
Verbs of Bodily Sensation "I feel bad" and "I am feeling bad" are virtually identical in meaning. | |||
ache | feel | hurt | itch |
Transitional Events Verbs Progressive forms indicate the beginning of an event, as opposed to the simple present tense. "She was falling out of bed [when I caught her]" as opposed to "She falls out of bed every night." | |||
arrive die | fall land | leave | lose |
Momentary Verbs Progressive forms indicate little duration and suggest repetition. She is hitting her brother. He is jumping around the house. | |||
hit jump | kick knock | nod | tap |
STATIVE VERBS | |||
Verbs of Inert Perception and Cognition* I detest rudabaga, but not I am detesting rudabaga. I prefer cinnamon toast, but not I am preferring cinnamon toast. | |||
abhor | guess | mind | satisfy |
Relational Verbs I am sick, but not I am being sick. I own ten acres of land, but not I am owning ten acres. My brother owes me ten dollars" but not My brother is owing me ten dollars. | |||
be* |
depend on |
involve |
possess |
*Kolln suggests that we think of the difference between stative and dynamic in terms of "willed" and "nonwilled" qualities. Consider the difference between a so-called dynamic adjective (or subject complement) and a stative adjective (or subject complement): "I am silly" OR "I am being silly" versus "I am tall." I have chosen to be silly; I have no choice about being tall. Thus "tall" is said to be a stative (or an "inert") quality, and we cannot say "I am being tall"; "silly," on the other hand, is dynamic so we can use progressive verb forms in conjunction with that quality.
The same applies to verbs. Two plus two equals four. Equals is inert, stative, and cannot take the progressive; there is no choice, no volition in the matter. (We would not say, "Two plus two is equalling four.") In the same way, nouns and pronouns can be said to exhibit willed and unwilled characteristics. Thus, "She is being a good worker" (because she chooses to be so), but we would say "She is (not is being) an Olympic athlete" (because once she becomes an athlete she no longer "wills it").
A University Grammar of English by Randolph Quirk and Sidney Greenbaum. Longman Group: Essex, England. 1993. (46-47). Used with permission.
Understanding English Grammar by Martha Kolln. 4rth Edition. MacMillan Publishing Company: New York. 1994. (89-90).