Learn Hardcore Turkish: Tuvalete gitmeden önce kapıyı kapatmalısın. - You should close the door before going to the toilet.

Tuvalet (“toilet”) takes the dative case suffix -e to indicate movement to somewhere. So tuvalete means “to the toilet.” If you used tuvalette, that would be the locative case (“in the toilet”), and tuvaleti would be the accusative (“the toilet” as a direct object).

What does gitmeden mean, and why is it -meden instead of -madan?

The suffix -meden is the negative gerund (“without doing…”). Combined with önce, it forms a temporal clause: gitmeden önce = “before going.” Because the verb root git- has the front vowel i, vowel harmony requires the front form -meden (rather than -madan).

Why is önce placed after gitmeden? Could I say önce gitmeden?

The fixed pattern for “before doing X” is [verb-meden] önce. Although you might see önce gitmeden in very poetic or emphatic contexts, standard Turkish always attaches önce after the -meden form.

Why is kapıyı in the accusative case?

In Turkish, a definite or specific direct object is marked with the accusative suffix. Kapı (“door”) here refers to a particular door (“the door”), so it becomes kapıyı. If it were indefinite (“a door”), you would just say kapı without the suffix.

What does the suffix -malısın in kapatmalısın express?

The suffix -malı / -meli expresses necessity or obligation (“must/should”), and -sın is the 2nd person singular ending. Together kapat-malısın means “you must/should close (it).”

Why isn’t sen (you) used in the sentence?

Turkish verbs carry person/number information in their endings. Here -sın already tells you it’s “you (singular),” so pronouns like sen are usually omitted unless you want extra emphasis.

How does the word order work between the time clause and the main clause?

Turkish is typically SOV, and adverbial clauses (like time clauses) come before the main clause. So you say tuvalete gitmeden önce (“before going to the toilet”), then kapıyı kapatmalısın (“you must close the door”).

How would I say “after going to the toilet, you must close the door”?

Use the positive gerund -dikten sonra for “after doing.”
• Tuvalete gittikten sonra kapıyı kapatmalısın.

Are there other ways to express “must” in Turkish?

Yes. Besides -malı / -meli, you can use:
• zorunda olmak: Kapıyı kapatmak zorundasın.
• gerekmek: Kapıyı kapatman gerekiyor.
Both of these also convey obligation (“you have to close the door”).