Bolul este plin cu apă.

Because -ul is the definite article in Romanian for many masculine and neuter singular nouns.

• bol = a bowl
• bolul = the bowl

Unlike English, Romanian usually adds the definite article to the end of the noun instead of putting a separate word like the before it.

So:

• bolul = the bowl

Bol is a neuter noun in Romanian.

That matters because neuter nouns behave:

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

So in the singular you get forms like:

• un bol = a bowl
• bolul = the bowl

And in the plural:

• două boluri = two bowls
• bolurile = the bowls

Este is the 3rd person singular form of the verb a fi = to be.

It means is here.

So:

• bolul = the bowl
• este = is
• plin = full

Romanian normally uses a fi just like English uses to be in sentences like this.

Yes. E is a very common shorter form of este in everyday Romanian.

So both are correct:

• Bolul este plin cu apă.
• Bolul e plin cu apă.

The version with este sounds a bit more full or careful; e is very common in normal speech.

Plin is an adjective meaning full, and it has to agree with the noun it describes.

Since bolul is singular and here behaves like a masculine/neuter singular noun, the adjective is:

• plin = masculine/neuter singular

Other forms include:

• plină = feminine singular
• plini = masculine plural
• pline = feminine/neuter plural

Examples:

• Paharul este plin. = The glass is full.
• Sticla este plină. = The bottle is full.
• Bolurile sunt pline. = The bowls are full.

In Romanian, plin cu is a common way to say full of something.

So:

• plin cu apă = full of water

The preposition cu usually means with, but after plin it often corresponds to English of in this kind of sentence.

Other examples:

• Camera este plină cu oameni. = The room is full of people.
• Paharul este plin cu suc. = The glass is full of juice.

You may also encounter plin de, which is also common:

• plin de apă
• plin de oameni

Both exist, though usage can vary by context and style.

Because here Romanian is talking about water as a substance, not the water as a specific identified thing.

• apă = water
• apa = the water

In a phrase like full of water, Romanian normally uses the indefinite/basic form:

• cu apă

If you said cu apa, it would usually mean something more specific, like with the water or full of the water in a particular context.

A simple learner-friendly pronunciation guide is:

BO-lul ES-te plin ku A-puh

A few notes:

• o is usually like the o in for or a clear rounded o
• u in cu sounds like oo in boot
• ă in apă is a short central vowel, something like the unstressed a in sofa

So apă is roughly:

A-puh

Also, Romanian pronunciation is generally more phonetic than English, so words are often pronounced close to how they are spelled.

The Romanian letter ă is a very common vowel. It sounds like a short neutral vowel, similar to the a in English about or sofa.

So:

• apă is pronounced roughly A-puh
• both ă sounds are short and unstressed

This sound is different from plain a, which is more like a in father.

Compare:

• a = open ah
• ă = short neutral uh

Yes, Romanian word order is somewhat flexible, but the normal neutral order here is:

• Bolul este plin cu apă.

If you change the order, it can sound marked, poetic, or context-driven. For a learner, the standard order is the best one to use.

So the safest structure is:

subject + verb + adjective + complement

That gives:

• Bolul = subject
• este = verb
• plin = adjective
• cu apă = complement

No, not in standard Romanian. In the present tense, Romanian normally keeps the verb to be in sentences like this.

So you say:

• Bolul este plin.
• Bolul e plin.

Not normally:

• Bolul plin. ❌

English and Romanian are similar here: both normally need is.

The plural would be:

Bolurile sunt pline cu apă.

Breakdown:

• bolurile = the bowls
• sunt = are
• pline = full for neuter plural nouns
• cu apă = with/of water

Notice the changes:

• bolul → bolurile
• este → sunt
• plin → pline

This shows both noun and adjective agreement in Romanian.