Protasis (if...)	Apodosis (then...)
ei + Imperfect Indicative	Imperfect Indicative + an
Negative: mh	Negative: ou

ei oi summacoi proshrconto, ouk anecwroumen an.
If the allies were coming, we would not be retreating.

ei mh hmaV efulasseV, enepipton an hmin.
If you were not protecting us, they would be attacking us.

 

Protasis (if...)	Apodosis (then...)
ei + Aorist Indicative OR ei + Imperfect Indicative	Aorist Indicative + an OR Imperfect Indicative + an
Negative: mh	Negative: ou

ei SwkrathV eipen, hkousa an.
If Socrates had spoken, I would have listened.

ei oi summacoi proshlqon, ouk anecwrhsamen an.
If the allies had come, we would not have retreated.

ei mh efulasseV hmaV, enepeson an hmin.
If you had not protected us, they would have attacked us.
 

Imperfect (continuous or repeated action)

ei SwkrathV elegen, hkouon an.
If Socrates had spoken (every day), I would have listened (every day).

ei oi summacoi proshrconto, ouk anecwroumen an.
If the allies had been coming, we would not have been retreating.

ei mh efulasseV hmaV, enepipton an hmin.
If you had not kept protecting us, they would have kept on attacking us.