Imperfect and aorist active indicative

Two past tenses, and the difference between them is not when the action happened. Both are past. The difference is how the writer chose to present it, which is what chapter 2 called aspect — and this is the chapter where that stops being theory.

The imperfect: inside the action

Built from the present stem, with two changes: an augment on the front and secondary endings on the back.

First person singular and third person plural are both ἔλυον. Nothing in the form separates them; the sentence has to.

The augment

An ἐ- on the front, marking past time in the indicative. Three things happen to it in practice.

If the verb already begins with a short vowel, that vowel lengthens instead of taking a prefix: ἀκούω → ἤκουον.

If it begins with a long vowel or a long diphthong there is nothing left to lengthen, so the past looks exactly like the present. εὑρίσκω keeps its εὑ- almost throughout — 72 of its 75 past forms do — and the ending is then the only thing telling you the tense. The other three show what the augment would look like if it could: ηὕρισκον at Mark 14:55 and Acts 7:11, beside an unaugmented εὕρισκον at Luke 19:48.

And with a compound verb the augment goes inside, after the preposition:

ἐξέβαλεν τὰ πνεύματα λόγῳ

"He cast out the spirits with a word." The verb is ἐκβάλλω; the augment has landed between ἐκ- and the stem. This is what makes compound verbs awkward to look up, because the form on the page no longer starts with the letters the lexicon lists.

What the imperfect is for

It is the past tense of the imperfective aspect: the camera inside the action rather than outside it. Ongoing, repeated, attempted, or simply held open.

ἄγγελοι προσῆλθον καὶ διηκόνουν αὐτῷ

"Angels came and were ministering to him." Both verbs are past, and they are not the same kind of past. προσῆλθον is aorist — the coming is presented as one whole thing. διηκόνουν is imperfect — the ministering is presented as going on. Most translations say were ministering or began to minister for exactly that reason.

Mark uses the imperfect constantly for vivid narrative. When an author switches between the two, the switch is usually doing something, and it is worth stopping to ask what.

The aorist: the whole thing at once

Augment, stem, a σα marker, and secondary endings.

The aorist presents the action as a single whole, viewed from outside. That is all it claims. It does not say the action was quick, or once only, or finished — those are things the sentence may tell you, and the tense does not.

This matters more than almost anything else in first-year Greek, because sermons are built on the opposite claim all the time. The aorist is not the once-for-all tense. It is the tense that declines to comment.

Second aorists: the same tense, a different shape

Everything above describes the first aorist, the one with the sigma. There is a second pattern, and it is not a variant or an exception — it is more than half of what you will actually read.

A second aorist takes an augment and the same secondary endings as the imperfect, with no sigma at all, on a changed stem. λέγω gives εἶπον; ἔρχομαι gives ἦλθον; βάλλω gives ἔβαλον; ὁράω gives εἶδον.

καὶ στὰς ὁ Ἰησοῦς ἐφώνησεν αὐτοὺς καὶ εἶπεν

"And Jesus stopped, called them, and said." Both verbs are aorist active indicative, third singular, and they look nothing alike. ἐφώνησεν has the sigma; εἶπεν has a stem you would not have predicted from λέγω.

εἰς τὰ ἴδια ἦλθεν

"He came to his own." Same tense again, same endings as an imperfect would take, and no sigma anywhere.

Two things follow, and both matter more than the label does.

The endings do not tell you the tense here — the stem does. ἔβαλον and ἔβαλλον differ by one lambda: the aorist against the imperfect of the same verb. That single letter is the whole distinction.

And you cannot look a second aorist up by its own spelling. εἶπεν is not under epsilon in a lexicon; it is under λέγω. This is what the principal parts are for, and it is why the third one is worth learning for the common verbs even though the drill for it feels like rote.

There is no difference in meaning. A second aorist is aorist, with exactly the aspect described above. It is a different way of building the same tense, kept by the verbs that have been in the language longest — which is why the commonest verbs are the irregular ones, here as in English.

εἰμί in the past

The verb to be has no aorist. It has an imperfect, and you will meet it constantly.

οὗτος ἦν ἐν ἀρχῇ πρὸς τὸν θεόν

"He was in the beginning with God." ἦν alone accounts for most of these 455 occurrences, and John 1 uses it to hold a state open rather than to report an event — which is the imperfective aspect doing exactly what this chapter has been describing.

ἦν δὲ ὥρα τρίτη

"And it was the third hour." Learn ἦν and ἦσαν first; between them they cover most of what you will see.

What to watch for

ἐδίδασκεν αὐτούς

"He was teaching them" — the sentence that opens the Sermon on the Mount. An aorist there would have presented the teaching as one whole thing and moved on. The imperfect presents it as under way, and everything that follows is what he was saying.

The traps are mechanical. ἔλυον is first singular or third plural, and you cannot tell from the word. A verb beginning with a long vowel has no visible augment, so an imperfect can look exactly like a present until you read the ending. And ἔβαλον against ἔβαλλον is one lambda between an aorist and an imperfect.

None of those can be reasoned out. They are recognised, and recognition comes from meeting them often, which is what the drills are for.