Bole me usta.

Because usta is grammatically plural in Serbian.

Even though it usually refers to one mouth, usta is a plural-only noun (pluralia tantum), similar in idea to English words like scissors or pants. Since the verb agrees with usta, you use the plural form:

• bole = hurt (plural)
• boli = hurts (singular)

So:

• Bole me usta. = My mouth hurts.

Not:

• Boli me usta. ❌

This is just how the noun works in Serbian. Usta is normally used only in the plural form, even when talking about one person's mouth.

So Serbian speakers say:

• usta = mouth

but grammatically it behaves like a plural noun.

That is why you also get forms like:

• Bole me usta.
• Otvorio je usta. = He opened his mouth.

To an English speaker, this feels strange at first, but it is completely normal in Serbian.

Me means me in the accusative form, and it marks the person who feels the pain.

The structure is basically:

• [thing that hurts] + hurts + [person]

So literally, Serbian is closer to:

• The mouth hurts me.

In this sentence:

• usta = the thing that hurts
• me = the person affected

This is the same pattern you see in many Serbian pain expressions:

• Boli me glava. = My head hurts.
• Bole me oči. = My eyes hurt.
• Boli me stomak. = My stomach hurts.

Because Serbian often does not use a possessive like my with body parts when the owner is already clear from the pronoun.

So instead of saying something like my mouth hurts, Serbian naturally says:

• Bole me usta.

The me already tells you whose mouth it is: mine.

This is very common with body parts:

• Boli me glava. = My head hurts.
• Bole me noge. = My legs hurt.

Using a possessive here would usually sound unnecessary unless you are emphasizing ownership.

Usta is the subject.

That may feel backward to an English speaker, because English often says:

• My mouth hurts.

But Serbian uses a structure more like:

• The mouth hurts me.

So:

• usta = subject
• me = object

A useful clue is the verb agreement:

• bole is plural
• therefore it agrees with usta

Yes, Usta me bole is also possible.

Serbian word order is more flexible than English, but the short pronoun me is a clitic, and clitics usually go in second position in the sentence or clause.

So these are possible:

• Bole me usta.
• Usta me bole.

Both mean essentially the same thing, but the emphasis can shift slightly.

• Bole me usta. often sounds like a straightforward statement of discomfort.
• Usta me bole. can sound a bit more like It’s my mouth that hurts.

For a learner, the main thing to remember is:

• me usually cannot stand just anywhere
• it tends to come early, in second position

Usually usta means mouth.

Depending on context, English may sometimes translate it as mouth or refer loosely to the mouth area, but if you specifically mean lips, Serbian more precisely uses:

• usne = lips

So:

• Bole me usta. = My mouth hurts.
• Bole me usne. = My lips hurt.

If the pain is specifically in the lips, usne is better.

Yes. It is very useful to learn boleti as a pattern for talking about pain.

The key idea is:

• the body part or thing is the grammatical subject
• the person feeling pain goes in the accusative

Examples:

• Boli me glava. = My head hurts.
• Boli me zub. = My tooth hurts.
• Bole me oči. = My eyes hurt.
• Bole me usta. = My mouth hurts.

Singular subject:

• boli

Plural subject:

• bole

So the verb changes according to the thing that hurts, not according to the person.

You could, but it means something slightly different and sounds less natural in everyday speech for this basic idea.

The most natural everyday way to say My mouth hurts is:

• Bole me usta.

If you say something like:

• Imam bol u ustima.

that is more like:

• I have pain in my mouth.

This can sound more formal, medical, or descriptive. For normal conversation, Bole me usta is the expression to remember.

Because in Bole me usta, usta is the subject, not a location phrase.

Compare these two ideas:

1. Bole me usta.
   = My mouth hurts.
   Here, usta is the thing that hurts.

2. Imam ranu u ustima.
   = I have a sore in my mouth.
   Here, u ustima means in the mouth, so it is a location.

So u ustima is used when you mean in the mouth, but usta by itself is used when the mouth itself is the thing being talked about.

In normal modern Serbian, usta is the standard word and is treated as a plural-only noun. Learners should simply memorize it that way.

So for practical purposes, just learn:

• usta = mouth
• it behaves grammatically as plural

That will help you produce correct sentences like:

• Bole me usta.
• Operi usta. = Wash your mouth / rinse your mouth.
• Otvorite usta. = Open your mouth.