9.3.1 Formation of the French conditional: conditionnel
présent
The ending for the conditionnel I is always the same, only the stem of verbs differs (but only a bit). Verbs ending in -er und -ir just add this conditionnel-ending to the infinitive. Verbs ending in -oir or -re omit everything of their original ending and just use the r.
Examples
acheter
(to buy)
sortir
(to go out)
end-
ing
j'(e)
achèterais
I would buy
sortirais
I would go out
-ais
tu
achèterais
you would buy
sortirais
you would go out
-ais
il / elle
achèterait
he/she would buy
sortirait
he/she would go out
-ait
nous
achèterions
we would buy
sortirions
we would go out
-ions
vous
achèteriez
you would buy
sortiriez
you would go out
- iez
ils / elles
achèteraient
they would buy
sortiraient
they would go out
- aient
entendre
(to understand)
mouvoir
(to move)
end-
ing
j'(e)
entendrais
I would understand
mouvrais
I would move
-ais
tu
entendrais
you would understand
mouvrais
you would move
-ais
il / elle
entendrait
he/she would understand
mouvrait
he/she would move
-ait
nous
entendrions
we would understand
mouvrions
we would move
-ions
vous
entendriez
you would understand
mouvriez
you would move
- iez
ils / elles
entendraient
they would understand
mouvraient
they would move
- aient
Since there is no rule without exception, just have a short look at the the irregular verbs for conditionnel
présent.