What is the difference between saying, “I studied” and, “I was studying”? Both are in the past time, but there is another difference. You may not be able to describe it, but if you are a native English speaker you can feel it.
The difference is what we call “aspect.” “I studied” is indefinite. It does not tell you anything about the nature of your studying. It doesn’t specify if you were studying over a period of time. It doesn’t specify if you studied regularly or repeatedly. It simply states a fact. “I studied.”
On the contrary, what does “I was studying” tell you? It describes the action as continuous, as an ongoing action (in past time). It tells the hearer or reader what you were involved in doing.
Some of the Greek tenses are quite specific. If you want to describe an action that occurs in the past and you do not want to say anything about its aspect, you use the aorist tense. But if you want to describe a past action and want to be explicit that it was a process (“I was studying” rather than “I studied”), then you use the imperfect aspect. This distinction takes some of the guesswork out of the translation process.
However, if you want to describe an action that happens in the present, there are not two Greek tenses. Only one. In other words, if you were to say manthano, it could be translated as either “I study” or “I am studying.” The translator has to make a decision with present tense verbs. Because English distinguishes between an undefined and a continuous action in the present tense, you have to use one or the other in translating a Greek present tense verb. Which one will it be?
