Închide ușa înainte să pleci.

Închide means close / shut here.

It is the 2nd person singular imperative of a închide = to close.
So it is used to give a command to one person, like:

• Închide ușa! = Close the door!

If you were speaking to more than one person, or using the polite form, you would usually say:

• Închideți ușa! = Close the door!

Romanian often puts the definite article at the end of the noun instead of using a separate word like the.

So:

• ușă = a door
• ușa = the door

In this sentence, ușa means the door.

Să is a very common Romanian particle used before a verb in certain subordinate clauses and verb constructions.

In înainte să pleci, it introduces the action you leave.

So:

• înainte = before
• să pleci = literally something like that you leave, but naturally: you leave

Together:

• înainte să pleci = before you leave

You should think of înainte să + verb as a normal Romanian pattern.

Because after înainte să, Romanian normally uses a conjugated verb, not the infinitive.

So:

• a pleca = to leave
• pleci = you leave

In this sentence, the subject is you, so Romanian uses the 2nd person singular present/subjunctive form:

• să pleci = that you leave / for you to leave / before you leave

Even though English says before you leave, Romanian does not use the infinitive here.

Formally, pleci is the same form you see in the present tense:

• tu pleci = you leave / you are leaving

After să, Romanian uses the subjunctive construction, but for many verbs the actual verb form looks identical to the present indicative.

So in:

• să pleci

the important thing is not just pleci by itself, but the whole structure să pleci.

Înainte usually means before or ahead / forward, depending on context.

In this sentence:

• înainte să pleci = before you leave

In other contexts, it can mean:

• Mergi înainte. = Go forward.
• Am ajuns înainte. = We arrived earlier / before the others.

So the exact meaning depends on the structure around it.

Yes. That is another very common way to say before leaving / before you leave.

Compare:

• Închide ușa înainte să pleci.
• Închide ușa înainte de a pleca.

Both are natural.

A rough difference:

• înainte să pleci focuses more directly on before you leave
• înainte de a pleca is a little more like before leaving

In everyday Romanian, both are used.

Pretty much, yes.

Romanian:

• Închide = Close
• ușa = the door
• înainte să pleci = before you leave

So the order is:

verb + object + time clause

just like English:

Close + the door + before you leave

That makes this sentence relatively straightforward for English speakers.

A simple approximate pronunciation is:

uhn-KEE-deh OO-sha uhn-AH-een-te suh PLECH

A few useful notes:

• î sounds somewhat like a close central vowel, not exactly like a typical English vowel.
• ch in închide is like k here.
• ș is sh
• ce/ci often sound like che/ch, so pleci sounds roughly like plech

If you want to sound more natural, pay attention to these words:

• ușa = OO-sha
• să = a short unstressed suh
• pleci = plech

Romanian often leaves out subject pronouns when they are already clear from the verb form.

So:

• pleci already tells you it means you leave
• închide here is a command to you

Because of that, Romanian does not need to say tu.

You could add tu for emphasis in some contexts, but normally it is omitted.

Yes, it is addressed to one person informally.

• Închide ușa înainte să pleci. = speaking to one person you call tu

For a polite singular or for plural you, Romanian would usually say:

• Închideți ușa înainte să plecați.

So the original sentence is the informal singular version.

Yes. In many contexts, a închide can be translated as either to close or to shut.

For example:

• Închide ușa. = Close the door. / Shut the door.

Romanian does not usually make a strong distinction between those two English choices here.

The dictionary forms are:

• a închide = to close
• a pleca = to leave

The sentence uses these forms:

• închide = imperative, close!
• pleci in să pleci = you leave

So when learning vocabulary, you would normally memorize:

• a închide
• a pleca