A bandeira tarifária está amarela.

A is the feminine singular definite article, meaning the.

It matches bandeira, which is a feminine singular noun in Portuguese:

• a bandeira = the flag

In Portuguese, articles are used very often, sometimes more often than in English, so a bandeira tarifária is the natural way to say the tariff flag.

Portuguese nouns have grammatical gender, and bandeira is a feminine noun. Its gender is fixed; it is not chosen based on meaning.

So you say:

• a bandeira
• not o bandeiro

This also affects the article and adjectives connected to it.

Tarifária is an adjective modifying bandeira.

So:

• bandeira = flag
• tarifária = tariff-related / billing-related

Together, bandeira tarifária is a set phrase in Brazilian Portuguese, especially in the context of electricity pricing. It refers to the color-coded rate system.

This is a good example of how Portuguese often places adjectives after the noun:

• bandeira tarifária = tariff flag

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

Here, está is used because the sentence is talking about the current state or status of the tariff flag. In other words, the flag is currently yellow.

• está amarela = it is yellow right now / it is in the yellow status

If you said é amarela, it would usually sound more like you are describing an inherent characteristic, such as the physical color of an object.

So in this context, estar is the natural choice.

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

The noun here is bandeira, which is feminine singular, so the adjective must also be feminine singular:

• masculine singular: amarelo
• feminine singular: amarela

So:

• a bandeira está amarela

If the noun were masculine, you would use amarelo instead.

Grammatically, it is a color adjective: yellow.

But in this sentence, the meaning is usually status, not just physical color. In Brazil, bandeira tarifária refers to a pricing category indicated by colors, so amarela means the tariff system is currently in the yellow category.

So the word itself is still the color yellow, but the sentence uses it as part of a coded system.

You can say it grammatically, but it usually changes the meaning or sounds less natural in this context.

• A bandeira tarifária está amarela = the tariff flag is currently yellow
• A bandeira tarifária é amarela = the tariff flag is yellow by nature / in essence / as a defining characteristic

Because this is a changing tariff category, está is the normal choice.

The subject is A bandeira tarifária.

The sentence breaks down like this:

• A bandeira tarifária = the tariff flag
• está = is
• amarela = yellow

So the structure is:

subject + verb + adjective

Portuguese often leaves out subject pronouns when they are not necessary, but in this sentence the subject is already explicitly stated: A bandeira tarifária.

English might think in terms of:

• The tariff flag — it is yellow

But Portuguese does not need an extra pronoun there. The noun phrase itself is the subject.

In Brazilian Portuguese, está is usually pronounced roughly like eh-STA or es-TA, with the stress on the last syllable.

A simple learner-friendly approximation is:

• está ≈ eh-STAH

The final á is stressed.

Yes, this is completely normal Portuguese word order.

The pattern is:

• article + noun + adjective + verb + adjective

More specifically:

• A = the
• bandeira = flag
• tarifária = tariff-related
• está = is
• amarela = yellow

It is very common in Portuguese for an adjective like tarifária to come after the noun:

• bandeira tarifária

And after estar, an adjective like amarela works just like in English:

• está amarela = is yellow

In the plural, the article, noun, verb, and adjective all change as needed:

• singular: A bandeira tarifária está amarela.
• plural: As bandeiras tarifárias estão amarelas.

Notice the agreement:

• a → as
• bandeira → bandeiras
• tarifária → tarifárias
• está → estão
• amarela → amarelas

This is a good example of how many parts of a Portuguese sentence change to match number and gender.