There are six major kinds of variation in the structure of verb phrases. Aspect is one of them. It has four types:
- unmarked or simple aspect
- perfect aspect
- progressive aspect
- perfect progressive aspect
The perfect aspect most often describes events or states taking place during a preceding period of time. The progressive aspect desribes an event or state of affairs in progress. Verb phrases can be marked for perfect and progressive aspects at the same time. On such and rare occasions they refer to a past situation or activity that was in progres for a period of time.
Perfect and progressive aspects can be combined with present or past tense.
Please tell me if you need more info.
- For Teachers