Obligation and prohibition
CEFR B1 · part 1
edumaterial's parts within the level. The European framework does not subdivide them.
When French needs the subjunctive (and when it does not)Forming the present subjunctive and, above all, knowing when it is not used even though…Past participle agreementAgreeing the participle with être always, and with avoir only when the direct object…Reporting what someone saidTurning a sentence into reported speech, changing tense, person and time or place markers.Connectors that are not synonymsChoosing the connector that says what you mean, knowing that ones from the same list are…The adjective that changes meaningPlacing six adjectives before or after depending on the meaning, and reading correctly…tout, chaque, quelque, plusieursChoosing the right form of tout, and not pluralising what is always singular.The rule, in three lines
Obligation: il faut + infinitive, il faut que + subjunctive, devoir. Prohibition: il ne faut pas, il est interdit de. And the trap: il ne faut pas is NOT «you don't have to», it is «you must not». For «not necessary» you need il n'est pas nécessaire de.
The usual slip. Reading il ne faut pas fumer as «you don't have to smoke». It means «you must not smoke»: a prohibition.
Why it catches you out. English keeps the two apart with different words: you don't have to is optional, you must not is forbidden. French uses one negation for what English splits, and it always lands on the second meaning.