Espera un moment.

Catalan often drops subject pronouns when they are clear from the verb form. Here, espera already tells you the speaker is addressing tu.

So:

• Espera un moment = Wait a moment
• Tu espera un moment is possible, but it sounds emphatic or contrastive, not neutral.

This is very common in Catalan.

Here it is a command: the imperative form of esperar for tu.

But espera can also be the present indicative form meaning he/she waits or you wait in some contexts. For example:

• Ella espera = She waits / She is waiting

So the form itself can mean more than one thing; context tells you which one it is. In Espera un moment, it is clearly an imperative.

You use Espera un moment with one person you address as tu: a friend, family member, child, classmate, etc.

Other versions are:

• Esperi un moment = formal singular
• Espereu un moment = informal plural
• Esperin un moment = formal plural

So espera is specifically the informal singular form.

Moment is a masculine noun in Catalan, so it takes un:

• un moment
• el moment

If it were feminine, it would take una, but that is not the case here.

This is basically the same pattern as English a moment, except Catalan nouns have grammatical gender.

Because Catalan normally says this without a preposition:

• Espera un moment
• Espera dos minuts
• Espera una mica

In English, wait a moment is also very natural, and Catalan works the same way here. You do not normally say espera per un moment in this sense.

Because in an affirmative command, Catalan usually puts the verb first:

• Espera un moment
• Mira això
• Vine aquí

That is the normal imperative pattern. You could add a subject for emphasis, but the basic structure is just verb + rest of the sentence.

A simple approximation is:

• Espera ≈ es-PE-ra
• un moment ≈ oon mo-MENT

A few useful notes:

• The stress in espera is on -pe-
• The stress in moment is on the last syllable
• The r in espera is a light tapped r, not the English r
• In many accents, the final t in moment is very weak or not clearly pronounced

Pronunciation varies somewhat by dialect, but that will give you a good starting point.

Because both words already follow the normal Catalan stress rules, so they do not need written accents.

• espera ends in a vowel, so the normal stress is on the penultimate syllable
• moment ends in a consonant, so the normal stress is on the last syllable

Written accents are mainly used when a word’s stress does not follow the expected pattern.

It is a normal, neutral everyday expression. It does not usually sound rude by itself, especially with people you know.

If you want to make it softer or more polite, you can add si us plau:

• Espera un moment, si us plau
• Esperi un moment, si us plau = more formal

Tone also matters a lot. Said gently, it sounds perfectly polite.

No. Like Spanish esperar, Catalan esperar can also mean to hope or to expect, depending on context.

For example:

• Espera un moment = Wait a moment
• Espero que vingui = I hope he/she comes
• L’esperava demà = I was expecting him/her tomorrow

So you should learn esperar as a verb whose exact meaning depends on the sentence.

Yes. Momentet is a diminutive of moment, and it can sound a bit softer or friendlier:

• Espera un momentet

You may also hear:

• Un moment! = One moment! / Just a moment!
• Espera una mica = Wait a bit

So Espera un moment is the basic form, but there are several natural everyday alternatives.