Conjugation pattern
Verbs in -yer

Verbs in -eyer

Verbs ending in -eyer are relatively few. The most frequent is "grasseyer" which means to pronounce certain consonants like r from the throat. In their case, the y is kept throughout the conjugation. This y cannot be replaced by an i.

je grasseye
tu grasseyes
il grasseye

Verbs in -ayer

There, the verbs are much more numerous. Examples include balayer, effrayer, essayer or payer (to sweep, to scare, to try or to pay). There are other less frequent verbs in the same pattern. These verbs can change the y into an i in front of a silent e. But they can also keep the same y. For them, we have a double conjugation.

je paie or je paye
nous essaierons or nous essayerons

A small remark about the verb "bayer" (familiar by the way) which means to keep your mouth open. This verb theoretically follows the same rule but it is only used in the expression "bayer aux corneilles", so it is only used in the infinitive. The more sustained verb is "bâiller" (to yawn) which is used to indicate a wide opening (of the mouth after falling asleep for example but also of a door). As long as we are on the remarks, do not confuse "bâiller" and "bailler". "Bailler" is a completely defective verb meaning to give. Once again, watch out for accents!

Verbs in -oyer and -uyer

We have seen the case of verbs that keep the y in conjugation and then hybrids (y and i). All we need now is this category: the verbs that change the y into an i before a silent e in the whole conjugation. This is the case of the verbs in -oyer and -uyer: aboyer (to bark), employer (to use), envoyer (to send), nettoyer (to clean), appuyer (to press), ennuyer (to bother), essuyer (to wipe)...

je nettoie (Indicative present)
nous nettoyons (Indicative present)
je nettoyai (Simple past)

Verbs envoyer and renvoyer

The only two exceptions to the -oyer verbs are "envoyer" (to send) and "renvoyer" (to return) which are irregular in the future tense and the present conditional.

j'enverrai (Simple future)
nous enverrions (Conditional present)

In brief

Here's a little chart to help you memorize all these rules more easily:

Finally, a short note about the conjugation of -yer verbs in general. In the first two persons of the plural of the imperfect, these verbs take an i after the y. This is not an exception in itself since it is the normal ending but it is a bit shocking at first. It is written as nous payions (we paid).