The Imperfect: Group 2

Group-2 (contracted) verbs build the imperfect on the distinctive -ούσα series rather than by taking an augment: αγαπώ → αγαπούσα, αγαπούσες, αγαπούσε, αγαπούσαμε, αγαπούσατε, αγαπούσαν. The stress sits on the -ού- throughout and never moves, and no augment is needed because the form is already long enough to carry the stress. The meaning is the ordinary imperfective past - ongoing or habitual - so the contrast with the Group-2 aorist αγάπησα is the same aspect contrast Group 1 makes between έγραφα and έγραψα. The tell for the whole group: if the present is end-stressed (αγαπώ, μιλάω), expect -ούσα (αγαπούσα, μιλούσα), not an έ-.