In linguistics, one of the main inflectional categories that can be applied to a verb. (The others being tense and mood.)
Aspect refers to the degree to which the action of the verb is complete. There is a general continuum of available aspects, with descriptions and examples given below:
pluperfect - this is an aspect in conjunction with a
past tense, and describes a case where the action of the verb was already completed or finished
before some other action. Example, "John had already left the house when Mary called."
perfect - describes a case where the action of the verb is completed or finished. Example, "Mary baked a cake."
imperfect - describes a case where the action of the verb is (or was) taking place, but is not yet finished or completed. Examples; "Mary is writing a letter"; "John was cleaning the room."
continuative - describes an action that is performed routinely, frequently, or often. Example, "John runs 5 miles every day."
In English, at least, aspect is fairly simply indicated. (For example, an imperfect aspect almost always involves some form of the verb "to be" followed by the gerund form of the verb... "is running", "was walking", "will be writing", etc.) Also, English grammar tends to make assumptions or have a "default" aspect based on the tense... past tense, with no explicit markers, usually indicates a perfect aspect {"John cleaned"), while present tense with no explicit markers usually indicated a continuative aspect ("Mary writes"). It is important to note, though, that in other languages, different assumptions about aspect may be made, and aspect itself may be marked or indicated in different ways.