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To add to the discussion above of aspect in linguistics: both the analysis and the terminology are endlessly debatable. Aspect can be a catch-all category for anything about a verb that defies neater analysis.

Some terms are highly overloaded: perfect and imperfect are the worst; these may be traditionally used in descriptions of Latin, Greek, English, French, German, Hebrew, Arabic, and Russian, but meaning slightly different things in each case. The terms perfective and imperfective are often used to try to get away from the traditional associations, but the improvement is limited.

Here are some aspectual variations that can occur in a language. Each language will be able to mark several of these distinctly, and the others will just come out by context. And don't hold me to any of these precisely.

And I could probably come up with more. The awkwardness in trying to make the difference clear in English reflects the fact that they overlap. But if necessary a distinction can be made, e.g.

"I rang my mother on Tuesday": semelfactive
"I rang my mother every Tuesday": habitual
"I kept on ringing my mother": frequentative
"I started reading Candide": inceptive
"I opened Candide": punctual
"I was reading Candide yesterday": continuous
"I read Candide last month": perfective

Examples could be multiplied indefinitely, with much disagreement.

Aspect is closely linked with Aktionsart (German for "kind of action"), which is the inherent aspectual property of a verb. "Know" is stative: it indicates a state; "receive", "suffer", "fall" are passive; "work", "walk" are active; and things like "sleep" and "grow" are fairly static actions, whose classification would depend on the language.

In languages like Russian and Polish, semelfactive and frequentative have different verbs (typically one is a modification of the other). This is pervasive in the Slavonic languages. But we can see how Aktionsart and aspect interact in English. You would think "see" is fairly straightforward in meaning: "Mary saw the pelican" is clear, isn't it?

Mary saw the pelican for six months but they eventually broke up and she now lives with a toucan. (durative)
Mary saw the pelican until it dwindled to a speck over the horizon. (continuous)
Mary saw the pelican when it emerged from the undergrowth. (punctual)
Mary saw the pelican when she forgot to take her medicine. (either punctual or aorist; if you change "when" to "whenever" or "if" it's definitely aorist)

Now go through them seeing if you can change "saw" to "was seeing", "could see", "used to see", "kept seeing", "has seen", "had seen", or "had been seeing" in each of those, and what difference if any it makes to the sense, and you'll see the range of aspect that can be expressed even in one language. (And note that they're all past tense.)

Then consider "look". Semantically it's virtually the same as "see", but its Aktionsart is quite different. "Mary looked at the pelican for ten minutes" is active on her part, "Mary saw the pelican for ten minutes" is stative or passive. And when it emerges from the bushes and Mary saw it, that's a single punctual act; whereas if she looked at it when it emerged, that's an inception of a continuous act.