Не забудь ремень, когда надеваешь брюки.

Don’t forget your belt when you put on your pants.

Breakdown of Не забудь ремень, когда надеваешь брюки.

• не: not
• когда: when
• забыть: to forget
• надевать: to put on
• ремень: belt
• брюки: pants

Questions & Answers about Не забудь ремень, когда надеваешь брюки.

Why is it Не забудь and not Не забывай?

Both are possible, but they have different “feel” (aspect + imperative meaning):

• Не забудь (perfective imperative) = make sure you don’t forget (this one thing this time); it points to a single result: you end up remembering the belt.
• Не забывай (imperfective imperative) = don’t be forgetting / don’t forget as a habit; it sounds more like a general repeated reminder.

So Не забудь ремень… is a natural “one-time” reminder.

What exactly is the form забудь?

Забудь is the 2nd person singular imperative of the perfective verb забыть (to forget).
It addresses ты implicitly:

• (ты) не забудь = don’t forget / make sure you remember
  For plural/polite вы, you’d use Не забудьте.

Why is there no word for you (like ты) in the sentence?

Russian normally omits subject pronouns when the verb ending already shows the person/number.
Here забудь and надеваешь clearly indicate you (singular), so ты is unnecessary unless you want emphasis/contrast (e.g., Ты не забудь… = You, don’t forget…).

Why is ремень in this form, and what case is it?

ремень is the direct object of (не) забудь, so it’s in the accusative.
For many masculine nouns, the accusative looks like the nominative (especially inanimate ones):

• ремень (Nom.) → ремень (Acc.)

Could I also say Не забудь про ремень? What’s the difference?

Yes, Не забудь про ремень is also common.

• Не забудь ремень = don’t forget the belt as an item (e.g., to take it / to use it).
• Не забудь про ремень = don’t forget about the belt (slightly more “about the idea/need” than about physically taking it).

Both can work here; the version without про often sounds more direct and “object-focused.”

Why is it когда надеваешь брюки (present tense) if it’s telling me what to do in the future?

In Russian, когда + present tense often expresses a general/typical situation: when(ever) you put on trousers. It doesn’t have to mean “right now.”

If you mean a specific future occasion, you might hear:

• когда будешь надевать брюки = when you’re going to put on your trousers (this time / in the future)

So когда надеваешь… is more like “as you do this (in general).”

Why is the verb надеваешь 2nd person singular, and what does it imply?

надеваешь is 2nd person singular present tense of надевать (to put on).
It matches the implied ты and gives a “whenever you do X” sense:

• когда надеваешь брюки = when you put on trousers / when you’re putting on trousers (as a routine)

What’s the difference between надевать and одевать? Which one is correct here?

The common rule is:

• надевать (что?) = put on a thing (clothes/accessories): надевать брюки, надевать ремень
• одевать (кого?) = dress someone: одевать ребёнка

So надеваешь брюки is correct because брюки is the thing being put on.

Why is there a comma before когда?

Because когда надеваешь брюки is a subordinate clause (“when…” clause). Russian separates the main clause and a subordinate clause with a comma:

• Не забудь ремень, когда надеваешь брюки.

You can also flip the order:

• Когда надеваешь брюки, не забудь ремень.

Why is брюки plural, and what case is it here?

брюки (trousers/pants) is a plural-only noun in Russian (like English pants).
After надевать, it’s the direct object, so it’s accusative plural—and for брюки, accusative plural looks the same as nominative plural:

• брюки (Nom. pl.) = брюки (Acc. pl.)