In English, we are familiar with the idea that verbs come in three tenses that show the time when an action happens:

      Present tense - something happening now

      Past tense - something that happened earlier, like yesterday

      Future - something that will happen later, like tomorrow

In Greek, verbs don't work the same way.  In plain statements of fact (known as the "indicative mood"), Greek verbs do tell you something about the time when an action takes place.  But that's not the most important concern.  Greeks were primarily interested in the type of action, not the time when it happened.  If you listen to scholars talking about this concept, you may hear the words "aspect" or "Aktionsart."  With minor distinctions, all these terms refer to the same set of ideas.  Let's explain it this way:

Greek verbs show three types of action:

1.  Continued action -- the verb describes someting that is going on continually or repeatedly.

2.  Simple action -- the verb merely tells you that something happened, without any extra information about how long it took or whether it has been completed.

3.   Completed action -- the verb describes an action that has been completed, and adds the thought that the results of the action continue afterwards.

Any of these three types of action can take place in the past, present or future.

For example, look at 1 Corinthians 3:6:  "I planted, Apollos watered, but God was causing the growth."

The first two verbs are aorist, which shows simple action.  Paul describes his time of ministry in Corinth as a single event: he planted. He emphasizes the fact that he planted, not how long he did it.  Paul chooses the same type of verb to describe Apollos' and his ministry there.

The third verb, however, is in the imperfect tense, which shows continued action: God was causing the growth.  This tense emphasizes the fact that God was quietly and constantly in action over the entire period of time.  Paul came and went; Apollos came and went.  But behind the scenes, God continually caused the church to grow.

 Another factor to consider when discussing verb tenses:  the characteristics of a verb tense may differ, depending on whether the verb is a statement of fact or one of the other "moods" such as imperative (command) or subjunctive.  Participles and infinitives also have their own rules for verb tense.

Take the aorist tense, for example.  We normally say that the aorist tense describes simple action in the past.  But we need to refine that statement a little:

Aorist tense definitely describes action in the past when the verb is in the indicative mode.The term "indicative" is a grammatical term used to describe a statement of fact.  When you work in the New Testament, most of the verbs are indicative, so it is natural to think of aorist as a past tense verb.  However, this is not the whole story.

Aorist tense describes simple action, but not necessarily action in the past when it is used in verb forms other than the indicative (such as imperatives, participles, or infinitives).

An aorist imperative, for instance, is a command.  It does not represent a command in the past.  If you go into your son's bedroom, shake the bed, and say, "Get up!" you aren't asking him to wake up yesterday.  You are telling him to do it right now.  If you were speaking Greek, you could use the aorist tense to rouse him, but the aorist command does not mean you want him to get up yesterday!  It just means you want him to do it - as a single action - right now!

The same principle applies to all the verb tenses, so it is important to notice whether a verb is in the indicative or some other form before you draw conclusions about the meaning of the verb tense.