il faut que + subjunctive
Week 16 gave il faut + infinitive, which tells everybody what to do. This gives il faut que + subjunctive, which tells one person what to do — and that difference is the reason to learn it.
| Il faut partir. | One must leave. / We should go. (nobody named) |
|---|---|
| Il faut que je parte. | I have to leave. |
| Il faut que tu viennes. | You have to come. |
| Il faut qu'elle soit là à huit heures. | She has to be there at eight. |
The infinitive version is impersonal advice; the que version assigns the obligation. In a conversation you almost always want the second.
The same split applies to the whole week 16 family:
| + infinitif | + que + subjonctif |
|---|---|
| il est important de partir | il est important que tu partes |
| il vaut mieux attendre | il vaut mieux que nous attendions |
| il est nécessaire de venir | il est nécessaire qu'il vienne |
The rule is simple: name the person → que + subjunctive. Leave them unnamed → de or nothing + infinitive.
The forms you will use ninety per cent of the time, and they are worth drilling as fixed blocks rather than derived each time:
| il faut que je sois | I have to be |
|---|---|
| il faut que je fasse | I have to do |
| il faut que j'aille | I have to go |
| il faut que je parte | I have to leave |
| il faut que tu viennes | you have to come |
| il faut que tu prennes | you have to take |
The negative still means "must not". Il ne faut pas que tu partes is a prohibition, exactly as in week 16 — not "you need not".
In speech the il disappears: faut que j'y aille is how a French person says "I've got to go", and it is probably the single most-heard subjunctive in the language.
Knowing the rule is not the same as producing it.
This page explains the pattern. The track drills it: the point arrives inside a mini-dialogue, then production marked against a CEFR descriptor, then a module test that returns you to your two weakest sessions if you miss it.