O cheiro do perfume é forte.

O is the masculine singular definite article, meaning the.

So o cheiro = the smell.

In Portuguese, articles are used more often than in English. A sentence like this usually sounds more natural with o than without it.

Cheiro means smell or scent.

It can be neutral, pleasant, or unpleasant depending on context. In this sentence, it simply means the smell/scent of the perfume.

A related verb is cheirar, which means to smell.

Do is a contraction of de + o:

• de = of
• o = the
• de + o = do

So:

• o cheiro do perfume = the smell of the perfume

This kind of contraction is very common in Portuguese.

Other common ones are:

• da = de + a
• dos = de + os
• das = de + as

In Portuguese, every noun has grammatical gender. Perfume is a masculine noun, so it takes o:

• o perfume

This grammatical gender does not mean the object itself is biologically male. It is just part of how the noun behaves in the language.

É is the he/she/it form of the verb ser in the present tense:

• ser = to be
• é = is

So:

• O cheiro do perfume é forte = The smell of the perfume is strong

Both ser and estar can mean to be, but they are used differently.

Here, é forte describes a quality of the smell: it is a strong smell. That is why ser sounds natural.

• é forte = it is strong / it has a strong quality

You may sometimes hear está forte in certain contexts, especially if someone is commenting on how strong it seems at the moment, but é forte is the more basic and expected choice in a simple descriptive sentence like this.

Forte is an adjective, and many Portuguese adjectives change to match gender and number. But forte is one of the adjectives that has the same form for both masculine and feminine singular.

So you get:

• o cheiro é forte
• a fragrância é forte

Both use forte.

It only changes in the plural:

• os perfumes são fortes
• as fragrâncias são fortes

In this sentence, forte is not directly attached to the noun. It comes after the verb é, so it works as a predicate adjective:

• O cheiro do perfume é forte
• literally: The smell of the perfume is strong

This is very normal in Portuguese, just as in English.

If you put the adjective before or right after the noun, you would be building a different structure.

Yes. O perfume é forte is a very natural sentence.

The difference is:

• O perfume é forte = the perfume itself is strong
• O cheiro do perfume é forte = the smell of the perfume is strong

The second version focuses specifically on the smell, while the first is a more general way to say essentially the same thing.

A rough English approximation is SHAY-roo, but not exactly.

A few details:

• ch in Brazilian Portuguese usually sounds like sh
• ei sounds somewhat like the ay in say
• the final o in many Brazilian accents sounds closer to oo than to a full English oh

So cheiro sounds approximately like SHEY-roo.

It can mean both, depending on context.

In this sentence, forte naturally means strong in the sense of having a strong smell.

So if someone says:

• O cheiro do perfume é forte

they usually mean the perfume smell is intense, noticeable, or possibly overpowering.

Yes, if the context already makes it clear what smell you mean.

• O cheiro é forte = The smell is strong

But if you want to specify that you are talking about the perfume’s smell, do perfume is important.

So:

• O cheiro é forte = general / context-dependent
• O cheiro do perfume é forte = specific

Yes, a few natural alternatives are:

• O perfume é forte.
• Esse perfume tem um cheiro forte.
• O cheiro desse perfume é forte.

These all sound normal, but they shift the emphasis a little:

• O perfume é forte focuses on the perfume overall
• tem um cheiro forte emphasizes that it has a strong smell
• desse perfume means of this perfume and makes it more specific in conversation