by George Valsamis
The tenses of a verb
THE CORE of the Greek tense system consists of the Present, Aorist and Present Perfect tenses. These tenses have more or less different stems, out of which all other tenses are formed (Imperfect uses the stem of the Present, Future uses the stem of the Aorist, Pluperfect and Future Perfect use the theme of the Present Perfect). That means, if you know the core of a verb, these three tenses, it's easy to find everything else.
In the course of time, as you become more familiar with the various verb forms, you will find it very easy to recognise the tenses. For the moment we need to say just a word about the meaning of tenses, how they define time in speech.
We say that Present refers to an action that happens now. In Greek it is called Ἐνεστώς = the time that has just now established/installed an action. Imagine this in space terms. When drawing a line, each point, one by one is established in and by time, and becomes instantly past. That very in-stant in which each point appears is the ἐν‑εστώς. In the sentence attributed to Heraclitus πάντα χωρεῖ καὶ οὐδὲν μένει (=everything moves and nothing remains), a sentence describing a principle, what gives the sense of a continuous present is just this, the sense of a principle, and not the meaning, of course. The principle as such is always present. We may call this a meta-present, a present that does not belong to a grammatical event, but to a detached observation of language and reality, as if the one who speaks was not governed by language or reality. It is interesting, that the very word ἐνεστώς is a present perfect participle, the very present is described by a present perfect word! We would be closer to reality if we talked not about present and present perfect, but about two forms of a present perfect, where present announces a probable present perfect, like saying “she plays” to mean “she has started to play”, some of her playing is already past!
Reference address : https://www.ellopos.net/elpenor/lessons/lesson2b.asp?pg=4