Breakdown of Il faut qu'il sache utiliser l'extincteur.
il
he
utiliser
to use
falloir
to be necessary / must (impersonal)
savoir
to know (a fact), to know how to
Questions & Answers about Il faut qu'il sache utiliser l'extincteur.
Why is sache used here instead of the present tense sait?
The phrase il faut que (it is necessary that) expresses an obligation or necessity. In French, this phrase always requires the verb that follows it to be in the subjunctive mood. Here, sache is the present subjunctive form of savoir (to know).
How do you form the subjunctive of savoir?
Savoir is one of the few verbs with a completely irregular subjunctive stem. Instead of borrowing its stem from the present tense, it uses a special root: sach-. You then add the regular subjunctive endings (-e, -es, -e, -ions, -iez, -ent). That is why the il form becomes il sache.
The English translation says "know how to use", but I don't see a word for "how" in the French sentence. Why?
When you want to say you know how to do a skill in French, you just use savoir followed directly by an infinitive verb. You do not add comment (how). So, savoir utiliser is the complete and natural way to say "to know how to use".
Could I just use devoir (must) to say this and avoid the subjunctive?