and three _Futures_, (1st and 2d, equivalent to each other, and
3d, very rarely used;) they are distinguished by certain letters
prefixed, inserted, or added to the stem or root of the verb. They
represent time as compared with the _present_, and never date
from that of a preceding verb.

§ 46. The Pres., Perf., Pluperf., and Fut. answer very nearly to the
same tenses in English.

§ 47. The Imperf. denotes an act as going on, but incomplete or
habitual at some time past: "was doing," etc.

§ 48. The Aorists indicate a single act at a definite time, (past in
the Indic., but undetermined in the others moods.)

§ 49. All the tenses with respect to form may be classed thus:--

I. _Primary_, or Absolute. Present. Perfect. Futures.

II. _Secondary_, or Historical. Imperfect. Pluperfect. Aorists.

These classes usually have the following endings respectively:--

Active Form. Persons. Middle and Passive.
I. II. I. II.
Pres. and Fut. Perf. Opt. Sing.
ο - ν μι 1st μαι μην
ις ς 2d σαι (σ)ο
ι - 3d ται το
Plur.