Group 1 spelling: -yer (y to i)
Summary
Verbs ending in -yer change the y to i before a silent e ending, but keep the y before the pronounced -ons and -ez endings; -ayer verbs may keep either spelling.
Explanation
Verbs ending in -yer are regular group 1 verbs whose stem ends in y, and they apply a spelling change keyed to the sound of the ending. The principle is simple: the y becomes i before a mute (silent) ending, but stays y when the ending is pronounced. The silent endings are -e, -es, -e and -ent, so a verb like nettoyer gives je nettoie, tu nettoies, il nettoie, ils nettoient; the audible endings are -ons and -ez, where the y is kept: nous nettoyons, vous nettoyez. The same pattern governs employer, ennuyer, appuyer, essuyer and envoyer.
Because the trigger is the silent ending and not the present tense as such, the y → i change also runs through the future and the conditional of -oyer and -uyer verbs, whose stem in those tenses ends in a silent e: je nettoierai, tu nettoieras … in the future and je nettoierais in the conditional. One verb breaks this neatly: envoyer is irregular in the future and conditional and does not simply add the endings to its infinitive — it gives j'enverrai, tu enverras, j'enverrais, which must be memorised separately.
Verbs ending in -ayer behave differently: they may keep either spelling. For payer, essayer and balayer, both je paie and je paye are accepted, as are je paierai and je payerai in the future. This optionality applies only to -ayer; with -oyer and -uyer the change to i is obligatory before a silent ending. Whichever -ayer spelling you choose, it is good practice to stay consistent within a text.
The main pitfalls cluster around the nous and vous forms and the optionality. First, do not change the y in nous and vous, where it is clearly pronounced: the correct forms are nous nettoyons and vous payez, not *nous nettoions or *vous paiez. Second, remember that -ayer verbs are not forced to change (writing je paye is not an error), and that the i of -oyer/-uyer verbs carries into the future and conditional — forgetting it and writing *je nettoirai is wrong.
Rule of thumb: before a silent e, y becomes i (je nettoie), but the nous and vous forms keep the y (nettoyons, payez); -ayer verbs may use either spelling, and the i of -oyer/-uyer verbs also appears in the future and conditional.
Examples
Je nettoie ma chambre, mais nous nettoyons le salon ensemble. — I clean my room, but we clean the living room together. (y → i before the silent -e (nettoie), but the y stays before the pronounced -ons (nettoyons).)
Tu paies l'addition ou tu payes ? Les deux sont corrects. — Are you paying the bill? Both spellings are correct. (Payer is an -ayer verb: je/tu paie and paye are both accepted.)
Ils emploient beaucoup de personnel dans cette usine. — They employ a lot of staff in that factory. (Employer (-oyer): y → i before the silent -ent (emploient).)
Je t'enverrai un message demain matin. — I will send you a message tomorrow morning. (Envoyer is irregular in the future: enverrai, not *envoierai.)
Nous essayons une nouvelle recette ce soir. — We are trying a new recipe tonight. (Essayer (-ayer): in the nous form the y is kept and pronounced (essayons).)
Common mistakes
Elle nettoye la cuisine.
Elle nettoie la cuisine.
For -oyer and -uyer verbs like nettoyer, the y must change to i before a silent ending such as the elle-form -e. Nettoye keeps the y, which is wrong here; the correct present form is nettoie. (This change is obligatory for -oyer/-uyer, unlike the optional y/i alternation allowed for -ayer verbs such as payer.)
Prerequisites
Related rules
spelling-changestem-changeorthography