The most stable part of the Greek verb is the stem (sometimes called the root). Many verbs have only one form for the stem; some have two; and a few have as many as six different forms. To these stems a series of regular endings are added in order to get the complete verb system. If one learns the six principal parts of a particular verb, then by attaching the various endings, one has full control over the verb.

The six principal parts are the indicative first person singular forms of:

1. Present Active
2. Future Active
3. Aorist Active
4. Perfect Active
5. Perfect Passive
6. Aorist Passive.

A Greek verb can have over 700 different forms (including participle forms). But the stem of all these forms will follow one of six principal parts. Listed below are the six principal parts, along with the verb forms that follow each part.

1. present indicative active 1st singular
   present (all)
   imperfect (all)
2. future indicative active 1st singular
   future active
   future middle
3. aorist indicative active 1st singular
   aorist active
   aorist middle
4. perfect indicative active 1st singular
   perfect active
   pluperfect active
5. perfect indicative middle/passive 1st singular
   perfect middle
   perfect passive
   pluperfect middle
   pluperfect passive
   future perfect passive
6. aorist indicative passive 1st singular
   aorist passive
   future passive