most common French infinitive verbs irregular stems ; futur simple tense

Avoir(to have)

aur-

Être(to be)

ser-

Faire(to do)

fer-

Pouvoir(to be able to)

pourr-

Savoir(to know)

saur-

Voir(to see)

verr-

Venir(to come)

viendr-

Devoir(to have to)

devr-

Vouloir(to want)

voudr-

Recevoir(to recieve)

recevr-

Envoyer(to send)

enverr-

Courir(to run)

courr-

Falloir(to need)

faudr-

Pleuvoir(to rain)

pleuvr-

acheter(to buy)

achèter

Aller(to go)

ir-

mourir (to die)

mourr-

devenir (to become)

deviendr-