Localul este plin vineri.

Because Romanian usually puts the definite article at the end of the noun, not before it.

• local = a venue / a place / a bar-like establishment
• localul = the venue / the place / the establishment

So -ul here is the masculine/neuter singular definite article.

Localul often means a venue, establishment, bar, pub, restaurant, or similar public place, depending on context.

It does not always mean just any place in the broad English sense. In everyday Romanian, local often suggests some kind of business or nightlife/social venue.

So in this sentence, it usually sounds like the bar / the venue / the place is full.

Este is the 3rd person singular of a fi = to be, so it means is.

• eu sunt = I am
• tu ești = you are
• el/ea este = he/she/it is

So localul este plin literally has the normal structure the venue is full.

In everyday speech, Romanians often use e instead of este:

• Localul e plin vineri.

That is more conversational, while este sounds a bit more neutral or formal.

Because the adjective has to agree with the noun.

Localul comes from local, which is a neuter noun. In Romanian, neuter nouns behave:

• like masculine in the singular
• like feminine in the plural

Since this sentence is singular, the adjective takes the masculine singular form:

• localul este plin

Compare:

• camera este plină = the room is full
• localul este plin = the venue is full

Romanian often uses the day of the week without a preposition in this kind of sentence.

So:

• vineri = on Friday

This is completely normal Romanian.

English needs on Friday, but Romanian does not need an equivalent of on here.

It can depend on context.

Localul este plin vineri can be understood as:

• The venue is full on Friday
• or sometimes more generally The venue is full on Fridays

If you want to make the habitual meaning clearer, Romanian often uses:

• vinerea = on Fridays
• în fiecare vineri = every Friday

So:

• Localul este plin vinerea. = The venue is full on Fridays.
• Localul este plin în fiecare vineri. = The venue is full every Friday.

Without extra context, vineri can be a little flexible.

No, Romanian word order is fairly flexible.

The basic order here is:

• Localul este plin vineri.

But you could also say:

• Vineri, localul este plin.

That puts more focus on Friday.

Both are correct. The original version is perfectly natural.

Normally, no. In standard Romanian, you need the copula a fi in this kind of sentence.

So:

• Localul este plin. = correct
• Localul e plin. = also correct, more conversational
• Localul plin. = not standard as a full sentence

So unlike some languages, Romanian normally does not drop is in the present tense here.

Yes.

• Localul este plin. = The venue is full.
• Localul este plin de oameni. = The venue is full of people.

Using just plin is very natural and often enough on its own. Adding de oameni makes it more explicit.

Yes, the final -i is part of the word and should be pronounced.

A rough English-friendly pronunciation would be:

• vee-NEER-y or vee-NER-ee, depending on how detailed you want to be

More exactly, Romanian r is usually a tapped/trilled sound, not an English r.

So vineri should not sound like English vine. The ending matters.

It is neuter.

That matters because Romanian neuter nouns behave:

• as masculine in the singular
• as feminine in the plural

So in the singular:

• localul este plin

But in the plural:

• localurile sunt pline = the venues are full

That is why you see plin here, not plină or pline.