Antes da festa, a Ana pôs batom vermelho.

Because antes normally takes the preposition de before a noun phrase: antes de = before.

Then de + a contracts to da in Portuguese:

• de + a festa → da festa

So antes da festa is the normal form in natural Portuguese.

In European Portuguese, it is very common to use the definite article before a person’s first name:

• a Ana
• o João

So a Ana simply means Ana, not the Ana in the English sense. This is a normal feature of Portuguese, especially in Portugal. In some more formal styles, the article may be omitted.

Pôs comes from the verb pôr, which means to put or to place.

Here, pôs is the 3rd person singular preterite:

• eu pus = I put
• tu puseste = you put
• ele/ela pôs = he/she put

So a Ana pôs means Ana put.

Because pôr is an irregular verb. Its past forms do not keep the same shape as the infinitive.

For example:

• pôr = to put
• põe = puts
• pôs = put
• pus = I put
• punha = was putting / used to put

This is something learners usually just have to memorize, like irregular verbs in English such as go → went.

The accent is part of the correct spelling and helps show the pronunciation of the stressed vowel.

So you should write:

• pôs

not:

• pos

It is also useful to think of it as belonging to the same verb family as pôr, which also keeps an accent in the infinitive.

Because the sentence describes a completed action:

• Antes da festa, a Ana pôs batom vermelho.
• Ana did this once, before the party.

The preterite (pôs) is the normal tense for a finished event.

If you used the imperfect, it would suggest something habitual, repeated, or backgrounded:

• A Ana punha batom vermelho antes da festa.

That sounds more like Ana used to put on red lipstick before the party or was putting on red lipstick before the party, depending on context.

Because Portuguese does not always match English phrasal verbs word for word.

In English, you say put on lipstick.
In Portuguese, you can simply say pôr batom.

So:

• pôr batom = to put on lipstick
• pôr perfume = to put on perfume
• pôr creme = to put on cream

The idea of applying something is already understood from the context.

Because Portuguese often allows a bare noun here when talking about makeup or a substance in a general way.

So pôs batom vermelho means she applied red lipstick, without focusing on a specific tube or item.

Compare:

• pôs batom vermelho = put on red lipstick
• pôs um batom vermelho = put on a red lipstick / a red shade
• pôs o batom vermelho = put on the red lipstick, a specific one already known

All three are possible, but the version without an article is very natural in this kind of sentence.

Because vermelho agrees with batom, not with Ana.

• batom is a masculine singular noun
• so the adjective must also be masculine singular: vermelho

That is why Portuguese says:

• batom vermelho

not:

• batom vermelha

The adjective describes the lipstick, not Ana.

Because in Portuguese, adjectives often come after the noun.

So the normal order is:

• batom vermelho = red lipstick
• casa grande = big house
• carro novo = new car

Putting the adjective before the noun is sometimes possible, but it is less neutral and can sound stylistic or change the nuance. Here, batom vermelho is the standard order.

The comma separates the introductory time expression from the main clause:

• Antes da festa, a Ana pôs batom vermelho.

This is very natural and helps readability. With short introductory phrases, Portuguese sometimes omits the comma, but using it here is perfectly normal.