A carta está na mesa.

Here, a means the, not a/an.

In Portuguese, a can be:

• the feminine singular definite article: the
• or the preposition to in other contexts

In A carta está na mesa, a carta means the letter.

If you wanted a letter, you would say uma carta.

Yes. Carta is a feminine noun in Portuguese, so it uses feminine words with it.

That is why you get:

• a carta = the letter
• uma carta = a letter

Many Portuguese nouns ending in -a are feminine, and carta is one of them.

Portuguese has two main verbs for to be: ser and estar.

In this sentence, está is used because it expresses location:

• A carta está na mesa = The letter is on the table

For physical location, Portuguese normally uses estar, not ser.

So:

• está = is in the sense of being located somewhere

Na is a contraction of:

• em = in/on/at
• a = the (feminine singular)

So:

• em + a = na

That means na mesa literally works like in/on the table, but in natural English here it is on the table.

This kind of contraction is very common in Portuguese.

The preposition em is broader than English in. Depending on context, it can correspond to:

• in
• on
• at

So na mesa is literally based on em, but with mesa the natural English translation is usually on the table.

Portuguese does not always separate in and on the same way English does.

The accent mark shows the stressed syllable and helps distinguish the correct written form.

• está = is
• stress falls on the final syllable: es-TÁ

That acute accent is important in standard spelling.

A simple approximate pronunciation for an English speaker is:

• ah KAR-tah es-TAH nah MEH-zah

A few notes for Brazilian Portuguese:

• carta: the r is not like a strong English r here; in many Brazilian accents it is softer or slightly breathy depending on position and region
• está: stress on tá
• mesa: the s sounds like z, so MEH-zah

A more natural connected rhythm may sound closer to:

• a KAR-ta es-TA na ME-za

Portuguese uses definite articles more often than English does.

So na mesa = on the table is the normal form.

Saying em mesa would usually sound wrong in this context. Portuguese generally wants the article here because you are talking about a specific table.

Yes. Sobre a mesa also means on the table.

Comparison:

• A carta está na mesa = the most common, natural everyday way
• A carta está sobre a mesa = also correct, sometimes a bit more explicit about being physically on top of the table

In many situations, both are fine.

This is the normal, neutral word order:

• subject + verb + location
• A carta
  • está
    • na mesa

Portuguese can change word order for emphasis, but this standard order is what learners should use first.

For example:

• Na mesa está a carta can exist in a more literary or emphatic context, but it is not the basic everyday pattern.

Usually, yes, carta commonly means a letter, especially a written letter.

But depending on context, carta can also mean things like:

• a card
• a menu, in some expressions
• a charter/document in formal contexts

In A carta está na mesa, the most natural meaning is a physical letter.

The article and the contraction would change.

For a masculine noun, you would often get:

• o = the (masculine singular)
• no = em + o

Example:

• O livro está no armário = The book is in the closet/cabinet

In your sentence:

• a carta is feminine
• na mesa is also feminine because mesa is feminine

So feminine grammar appears twice in the sentence.

Normally, no. In standard Portuguese, you would usually need the article or another determiner there.

Natural forms would be:

• A carta está na mesa = The letter is on the table
• Uma carta está na mesa = A letter is on the table

Without an article, it sounds incomplete in normal usage.

The base form is estar, meaning to be.

Está is the third-person singular form in the present tense, used with:

• ele = he
• ela = she
• você = you
• and singular nouns like a carta

So:

• A carta está... = The letter is...

Yes, in a broad sense. Using estar suggests the letter is currently located there.

That does not necessarily mean it will move soon, but it presents location as a state or position, not as an essential characteristic.

That is why estar is the normal verb for where something is:

• A carta está na mesa = the letter is there now / is located there

You can break it down like this:

• A = the (feminine singular article)
• carta = letter
• está = is
• na = in/on/at the = em + a
• mesa = table

So the structure is:

• A carta = subject
• está = verb
• na mesa = location phrase

This is a very common and useful sentence pattern in Portuguese.