Se o tomate estiver muito caro, a gente vai comprar batata e frango.

Se means if and introduces a condition.

So Se o tomate estiver muito caro... means If tomatoes are very expensive...

This is a conditional sentence:

• condition: se o tomate estiver muito caro
• result: a gente vai comprar batata e frango

In Portuguese, se is the normal word for if in this kind of sentence.

Because after se referring to a possible future situation, Portuguese usually uses the future subjunctive.

So:

• Se o tomate está muito caro sounds wrong for this meaning
• Se o tomate estiver muito caro is the correct structure for If tomatoes are expensive

This is a very common pattern in Portuguese:

• Se eu tiver tempo... = If I have time...
• Se ele puder... = If he can...
• Se chover... = If it rains...

So estiver is the future subjunctive form of estar.

In Portuguese, prices are usually expressed with estar:

• O tomate está caro.
• A gasolina está barata.

This is very natural in Brazilian Portuguese. It treats the price as a current condition or state.

Using ser here would usually not sound right for ordinary price comments.

So:

• está caro = is expensive
• estiver caro = is expensive / turns out to be expensive, in a future or hypothetical situation

A gente usually means we in everyday Brazilian Portuguese.

It is extremely common in speech and informal writing.

Examples:

• A gente vai comprar = We are going to buy
• A gente gosta de praia = We like the beach

Even though it means we, it takes a singular verb:

• a gente vai, not a gente vamos

So in this sentence:

• a gente vai comprar = we are going to buy

Because grammatically a gente behaves like a third-person singular expression.

So Portuguese says:

• A gente vai
• A gente compra
• A gente quer

Not:

• A gente vamos
• A gente compramos

This is one of the first things learners need to get used to:
a gente = plural meaning, singular grammar.

Vai comprar is the periphrastic future, literally is going to buy, and it is extremely common in Brazilian Portuguese.

So:

• a gente vai comprar = we’re going to buy / we will buy

The simple future comprará exists, but in everyday Brazilian Portuguese it often sounds more formal, written, or less conversational.

Compare:

• A gente vai comprar batata e frango. = very natural in speech
• A gente comprará batata e frango. = grammatically correct, but less common in everyday conversation

Portuguese often omits the article when talking about something in a general, non-specific way, especially after verbs like comprar.

So:

• comprar batata e frango = buy potatoes and chicken

This sounds like buying those items in general, not specific previously mentioned ones.

You could also hear:

• comprar batata e frango
• comprar batatas e frango
• comprar umas batatas e um frango

The exact form depends on how specific the speaker wants to be.

Not necessarily. In Portuguese, a singular noun can sometimes refer to a product or category in a general sense.

So o tomate estiver muito caro is often understood as:

• tomatoes are expensive
• tomato is expensive as a product

This is similar to how languages sometimes use the singular to talk about something generally.

In real life, Brazilians may also say:

• Se o tomate estiver muito caro...
• Se os tomates estiverem muito caros...

Both are possible, but the singular is very natural when talking about the item as a market product.

Because caro agrees with tomate, and tomate is masculine singular.

So:

• o tomate → caro
• a batata → cara
• os tomates → caros
• as batatas → caras

Muito here works like very, so it does not change:

• muito caro
• muito cara
• muito caros
• muito caras

The adjective changes, but muito stays the same when it means very.

Usually here it means chicken meat / chicken to eat.

In shopping and food contexts, frango commonly refers to chicken as food:

• comprar frango
• fazer frango no forno
• comer frango

Depending on context, it can also refer to a chicken animal, but in this sentence the food meaning is the obvious one.

Yes. Both are correct.

• A gente vai comprar batata e frango.
• Nós vamos comprar batata e frango.

The difference is mostly tone:

• a gente = more conversational, very common in Brazil
• nós = also correct, sometimes a bit more formal or careful depending on the situation

In everyday spoken Brazilian Portuguese, a gente is often more natural.

Yes. Portuguese allows some flexibility.

For example:

• Se o tomate estiver muito caro, a gente vai comprar batata e frango.
• A gente vai comprar batata e frango se o tomate estiver muito caro.

Both mean basically the same thing.

When the se clause comes first, a comma is normally used:

• Se o tomate estiver muito caro, ...

When it comes second, the comma is often omitted:

• A gente vai comprar batata e frango se o tomate estiver muito caro.

The sentence follows a very common Portuguese pattern:

Se + future subjunctive, main clause with future meaning

In this sentence:

• Se o tomate estiver muito caro → if tomatoes are expensive
• a gente vai comprar batata e frango → we’ll buy potatoes and chicken

You will see this same structure all the time:

• Se eu tiver dinheiro, vou viajar.
• Se ela puder, vai ajudar.
• Se chover, a gente fica em casa.

So this sentence is a great model for forming real-life future conditions in Portuguese.