No supermercado, eu comprei tomate e cebola.

No is a contraction of em + o:

• em = in / at
• o = the

So:

• em o supermercado → no supermercado

Portuguese uses these contractions very often. Here, no supermercado means in the supermarket or at the supermarket.

Because supermercado is a masculine noun, it takes o, not a. That is why it is no supermercado, not na supermercado.

The comma separates the opening location phrase from the main part of the sentence.

• No supermercado, eu comprei tomate e cebola.

This is similar to English sentences like:

• At the supermarket, I bought tomatoes and onions.

The comma is natural because No supermercado has been moved to the front for emphasis or framing. You could also say:

• Eu comprei tomate e cebola no supermercado.

That version is also correct and very common.

Not always. Portuguese often drops subject pronouns when the verb already makes the subject clear.

• comprei already means I bought

So both of these are correct:

• Eu comprei tomate e cebola.
• Comprei tomate e cebola.

Including eu can add clarity, emphasis, or contrast. For example, if you want to stress that I was the one who bought them, eu is useful.

Comprei is the 1st person singular form of the verb comprar in the pretérito perfeito (the simple past / preterite).

It means:

• I bought

Conjugation of comprar in this tense:

• eu comprei = I bought
• você/ele/ela comprou = you/he/she bought
• nós compramos = we bought
• vocês/eles/elas compraram = you all/they bought

So in this sentence, comprei tells you the action was completed in the past.

In Portuguese, food items are often used in the singular when talking about them in a general or non-count-specific way.

So:

• comprei tomate e cebola

can sound like:

• I bought tomato and onion
• or more naturally in English, I bought tomatoes and onions

Portuguese often treats these as grocery items or ingredients rather than focusing on the exact number.

If you want to emphasize separate countable items, the plural is also possible:

• Comprei tomates e cebolas.

Both are correct, but the singular is very natural in shopping contexts.

Portuguese often omits articles with foods or products when listing what someone bought, especially in a general sense.

So:

• comprei tomate e cebola

is a very natural way to say what was bought.

You could sometimes hear articles in other contexts, but here they are not needed. The sentence is presenting the items almost like a shopping list.

Compare:

• Comprei tomate e cebola. = I bought tomato and onion / tomatoes and onions.
• Comprei o tomate e a cebola. = I bought the tomato and the onion.

The version with articles sounds more specific, as if particular tomato and onion had already been identified.

• tomate is masculine: o tomate
• cebola is feminine: a cebola

This matters when you use articles or adjectives with them:

• o tomate vermelho = the red tomato
• a cebola roxa = the red/purple onion

Even though the sentence does not include articles before these nouns, it is still important to know their gender for other situations.

Yes, absolutely. That is a very normal word order.

Compare:

• No supermercado, eu comprei tomate e cebola.
• Eu comprei tomate e cebola no supermercado.

The difference is mainly emphasis:

• No supermercado, ... puts the location first.
• Eu comprei ... no supermercado sounds more neutral.

Both are correct and natural.

It can mean either one, depending on context. In many everyday situations, English might say at the supermarket, while Portuguese uses em/no supermercado.

So no supermercado can cover both ideas:

• physically in the supermarket
• more generally at the supermarket

This is very common with places in Portuguese.

In Brazilian Portuguese, comprei is roughly pronounced like:

• kom-PRAY

More carefully:

• com sounds like kong without a full g, depending on accent
• prei rhymes roughly with English pray

The stress is on the last syllable:

• com-PREI

A learner-friendly approximation is kohm-PRAY.

Portuguese often leaves that idea unexpressed when it is obvious from context.

English commonly says:

• I bought some tomatoes and onions.

Portuguese usually just says:

• Comprei tomate e cebola.

The meaning of some is understood naturally. If needed, Portuguese can express quantity more explicitly, for example:

• Comprei alguns tomates. = I bought some tomatoes.
• Comprei um pouco de cebola. = I bought some onion / a little onion.

But in a simple grocery sentence, tomate e cebola is enough.

Supermercado is a masculine noun in standard Portuguese, so it normally takes:

• o supermercado
• no supermercado
• um supermercado

It is not normally used as a feminine noun. So na supermercado would be incorrect in standard usage.

Yes. That is one reason tomate and cebola appear without articles and in the singular. It has a very natural grocery-shopping feel, almost like naming categories of items purchased.

It sounds like:

• At the supermarket, I bought tomato and onion.

In idiomatic English, we usually translate that more naturally as:

• At the supermarket, I bought tomatoes and onions.

So the Portuguese structure may feel a little different from English, but it is very common and natural.