A ameaça é grave.

Here A means the, not a/an.

In Portuguese, a can be:

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

In A ameaça é grave, ameaça is a feminine singular noun, so A ameaça means the threat.

If you wanted a threat, you would say Uma ameaça.

Portuguese nouns have grammatical gender, and ameaça is a feminine noun. That is why it takes the feminine article a:

• a ameaça = the threat

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

A learner usually just has to memorise the gender together with the noun:

• ameaça → feminine

É is the 3rd person singular of the verb ser (to be) in the present tense.

So:

• é = is

In this sentence:

• A ameaça = the subject
• é = is
• grave = serious / severe

The verb agrees with the singular subject ameaça, so we use é, not são.

This is a very common question because Portuguese has two verbs for to be: ser and estar.

Here ser is used because grave describes the nature or seriousness of the threat. It is presenting it as a characteristic or assessment:

• A ameaça é grave = The threat is serious

If you used estar, it could suggest a temporary state or condition in a different kind of context. In many cases with grave, both verbs can exist, but they do not always sound the same.

In this sentence, é grave is the most natural way to express that the threat is serious.

In this sentence, grave comes after the verb, not directly after the noun:

• A ameaça / é / grave

This is the normal structure:

• subject + verb + adjective

Portuguese often places adjectives after nouns when they directly modify a noun, but here grave is a predicate adjective after ser, so it naturally comes after the verb.

Compare:

• uma ameaça grave = a serious threat
• A ameaça é grave = The threat is serious

For gender, grave does not change:

• uma ameaça grave
• um problema grave

It works for both masculine and feminine singular.

For the plural, it does change:

• singular: grave
• plural: graves

So:

• A ameaça é grave = The threat is serious
• As ameaças são graves = The threats are serious

In European Portuguese, ameaça is pronounced approximately like:

• a-me-A-ça

A rough English-friendly guide could be:

• uh-meh-AH-suh

A few important points:

• The stress is on a in the middle: ameaça
• ç is pronounced like s
• The final a in European Portuguese is often reduced, not a strong open a

So ameaça does not sound like the English word threat at all; it has four syllables.

The ç is called c cedilha.

It tells you that the c is pronounced like s before a, o, or u.

So:

• ameaça sounds with an s sound, not a k sound

Compare:

• ca normally sounds like ka
• ça sounds like sa

That is why ameaça is pronounced roughly ameassa, not ameaka.

The accent in é is part of the spelling of that verb form. It helps distinguish it from e, which means and.

So:

• é = is
• e = and

Grave does not need a written accent because its stress pattern follows normal Portuguese spelling rules.

So the accent in this sentence is not optional:

• correct: A ameaça é grave
• incorrect: A ameaça e grave

The plural version is:

• As ameaças são graves.

Changes:

• A → As
• ameaça → ameaças
• é → são
• grave → graves

So every part that needs to agree changes appropriately.

Yes. Grave can have a few related meanings depending on context, such as:

• serious
• severe
• grave
• sometimes even low-pitched/deep in sound-related contexts

In A ameaça é grave, the natural meaning is serious or severe.

So even if the English translation shown to the learner is The threat is serious, it is useful to know that grave can be used in other contexts too.