O estilo é moderno.

O is the masculine singular definite article in Portuguese, meaning the.

So:

• o estilo = the style

Portuguese uses definite articles more often than English does, so it is very normal to say o estilo here.

É is the he/she/it form of ser (to be), and it is used for things seen as general, defining, or permanent qualities.

In O estilo é moderno, the sentence is describing what kind of style it is, so ser is the natural choice.

• ser = for identity, classification, essential characteristics
• estar = for states, conditions, locations, temporary situations

So O estilo é moderno means the style is modern in a descriptive, general sense.

É is the 3rd person singular present of ser.

Full present tense of ser:

• eu sou = I am
• tu és = you are
• ele/ela/você é = he/she/you are
• nós somos = we are
• vós sois = you are (old/literary)
• eles/elas/vocês são = they/you are

Here, o estilo is singular, so the verb is é.

Because estilo is a masculine singular noun.

In Portuguese, adjectives usually agree with the noun they describe in gender and number.

So:

• o estilo moderno = the modern style
• os estilos modernos = the modern styles

If the noun were feminine singular, the adjective would normally change:

• a decoração moderna = the modern decoration

One clue is the article: o estilo. The article tells you the noun is masculine singular.

Also, many nouns ending in -o are masculine, though this is a pattern, not a perfect rule.

So in this sentence, the clearest evidence is:

• o → masculine singular
• therefore estilo is masculine singular

Yes, but it means something slightly different in structure.

• O estilo é moderno. = The style is modern.
• O estilo moderno = the modern style

In the original sentence, moderno comes after é because it is the predicate adjective of the sentence. Without the verb, it becomes part of a noun phrase instead.

Yes, in this sentence it is very similar:

• O estilo = the style
• é = is
• moderno = modern

So the pattern is:

subject + verb + adjective

This is one of the reasons the sentence feels straightforward for English speakers.

In European Portuguese, é is pronounced like an open eh sound.

A rough guide:

• é ≈ eh

The accent mark is important because it shows both stress and vowel quality.

So é is not the same as an unstressed e in Portuguese.

Yes, but in European Portuguese the final -o is usually reduced and sounds more like u or a very weak close vowel.

So moderno does not end with a strong English oh sound.

A rough European Portuguese pronunciation guide might be:

• moderno ≈ muh-DER-nu

That is only approximate, but it helps show that the last vowel is weaker than English speakers often expect.

Normally, no. Estilo é moderno sounds incomplete or unnatural in standard Portuguese.

You would usually say:

• O estilo é moderno. = The style is modern.

Portuguese generally prefers the article here when referring to a specific noun like the style.

After the verb, yes, in this sentence:

• O estilo é moderno.

When used directly with a noun, adjectives in Portuguese often come after the noun:

• um estilo moderno = a modern style

Some adjectives can come before the noun, but moderno is very commonly placed after it in ordinary descriptive use.

The plural would be:

• Os estilos são modernos. = The styles are modern.

Notice the changes:

• o → os
• estilo → estilos
• é → são
• moderno → modernos

Everything agrees in number.