Learn Hardcore French: Tu dois consulter ton agenda avant le rendez-vous. - You must check your planner before the appointment.

It expresses a clear obligation. In everyday speech it often feels like "you need to" or "you have to," but it can be as strong as "you must" depending on tone and context.

Why isn’t it "tu dois de consulter"? Do we add "de" before an infinitive after "devoir"?

No. Modern French uses devoir + infinitif directly: Tu dois consulter… Adding de is incorrect here. Compare:

Correct: Tu dois consulter ton agenda.
Incorrect: ~~Tu dois de consulter ton agenda.~~ Some other verbs do take de (e.g., essayer de consulter), but devoir does not.

Can I say "Il faut que tu consultes ton agenda" instead? What’s the difference?

Yes. Il faut que tu consultes… uses the impersonal verb falloir and the subjunctive (consultes). It frames the necessity more generally/impersonally. Tu dois… targets the person directly and can feel more direct.

Why "tu" and "ton" instead of "vous" and "votre"? How would it change?

Tu/ton is informal singular. For formality or addressing more than one person, use vous/votre:

Informal: Tu dois consulter ton agenda…
Formal/plural: Vous devez consulter votre agenda… Also note: ton is used because agenda is masculine singular. For feminine nouns starting with a vowel, French still uses mon/ton/son (e.g., ton amie) to ease pronunciation.

Does "agenda" mean the same as English "agenda"?

Not exactly. In French, un agenda is your personal diary/planner/schedule book. The English sense "list of topics for a meeting" is usually un ordre du jour.

Is "consulter" natural here? Could I use other verbs?

Yes, consulter son agenda is idiomatic and slightly formal. Alternatives:

Neutral: regarder ton agenda (to look at your calendar)
Checking for accuracy: vérifier ton agenda
Informal: jeter un œil à ton agenda Note that consulter is also used with professionals (e.g., consulter un médecin), but here it just means "check."

Why "avant le rendez-vous"? Can I drop the article?

You need the article. French nouns almost always take an article: avant le rendez-vous. You can also make it more specific with a possessive: avant ton rendez-vous / avant votre rendez-vous. Dropping the article (~~avant rendez-vous~~) is incorrect.

When do I use "avant," "avant de," and "avant que"?

avant + noun/pronoun: avant le rendez-vous
avant de + infinitif: avant de partir, avant d’appeler
avant que + subjonctif: avant que le rendez-vous (ne) commence With avant que, use the subjunctive; the optional ne is stylistic (ne explétif).

Can I move the time phrase to the front?

Yes. Avant le rendez-vous, tu dois consulter ton agenda. Add a comma after the fronted time phrase.

Any pronunciation tips for this sentence?

tu dois: pronounce like “tu dwa”; the final -s of dois is silent.
ton agenda: make a liaison: say an audible n between words → “to-n agenda.” agenda has a soft j like the s in “measure” (a-zhɛn-da), and the en is nasal.
rendez-vous: three syllables “ran-de-vou” with a French r; the final -z in rendez is silent here.

Why is there a hyphen in "rendez-vous," and do I pronounce the "z"?

It’s a fixed compound noun spelled with a hyphen: rendez-vous. The final -z of rendez is not pronounced in this noun; say ran-de-vou, not “ran-dez-vou.”

Is "rendez-vous" masculine or feminine?

Masculine: le rendez-vous, un rendez-vous, ce rendez-vous. The plural is des rendez-vous (spoken the same as the singular).

Could I use the imperative instead of "tu dois…" to give a direct instruction?

Yes:

Informal: Consulte ton agenda avant le rendez-vous.
Formal/plural: Consultez votre agenda avant le rendez-vous. Imperatives are common in instructions and checklists.

How can I soften the tone (make it a suggestion)?

Use:

Tu devrais consulter ton agenda… (You should…)
Pense à consulter ton agenda… (Remember to…)
N’oublie pas de consulter ton agenda… (Don’t forget to…)

How do I make it very polite in a professional message?

Veuillez consulter votre agenda avant le rendez-vous.
Merci de consulter votre agenda avant le rendez-vous.
Nous vous prions de consulter votre agenda avant le rendez-vous.

How do I express future obligation?

Future simple: Tu devras consulter ton agenda… (You will have to…)
Near future: Tu vas devoir consulter ton agenda… (You’re going to have to…)
Both are correct; the near future sounds more immediate/conversational.

How does negation work with "devoir" here?

Tu ne dois pas consulter ton agenda… = You must not check your calendar (prohibition).
To express lack of necessity: Tu n’as pas besoin de consulter ton agenda…
To keep the positive idea (“don’t forget to check”), use: N’oublie pas de consulter ton agenda…

Can I omit the subject like in English “Must check calendar”?

No. French requires the subject pronoun: Tu dois consulter… If you want to avoid the subject, use the imperative: Consulte ton agenda…

Is "avant de le rendez-vous" ever correct?

No. avant de must be followed by an infinitive or a pronoun, not a full noun phrase. Use:

avant le rendez-vous (noun)
avant de le voir (pronoun + verb)
avant de partir (infinitive)

Why "le rendez-vous" and not "un rendez-vous"?

Le points to a specific appointment known from context. If you mean “before any appointment/in general,” use un: avant un rendez-vous, consulte ton agenda.