Astuce pour choisir entre verbe en -er ou en -é

How do you know whether to write “-er” or “-é” in French?

French -er verbs sound identical in the infinitive (manger) and the past participle (mangé), so by ear the spelling is a coin flip. The standard native fix is to swap in a verb from another group, usually vendre. If vendre fits the sentence, the spelling is -er; if only vendu fits, it is -é. Je veux manger → je veux vendre works, so -er. J’ai mangé → j’ai vendu works, so -é.

Mordre / mordu works the same way and is the version many French teachers use. The test works because third-group verbs have an infinitive and a participle that sound clearly different, so the ear can hear which slot the sentence needs — something -er verbs never let you do. The same logic explains why je vais manger takes the infinitive: je vais vendre is fine, je vais vendu is not.