Form: have + been + ing (present participle)
Meaning: The perfect progressive tenses give the idea
that one event is in progress immediately
before, up to, until another time or event. The tenses are used to express
the duration of the first event.
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Present Perfect Progressive
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a. Tom has been studying for
two hours.
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Event in progress: studying. When? Before now, up to now. How long? For two
hours.
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Past Perfect Progressive
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b. Tom had been studying for
two hours before his friend came.
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Event in progress: studying. When? Before another event in the past. How long?
For two hours.
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Future Perfect Progressive
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c. Tom will have been studying for
two hours by the time his friend arrives.
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Event in progress: studying. When? Before another event in the future. How
long? For two hours.
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