A corrente está suja.

Portuguese usually uses estar for temporary states or conditions, and ser for more permanent characteristics.

So A corrente está suja means the chain is dirty right now / in its current state.

If you said A corrente é suja, it would sound more like dirtiness is a defining characteristic of the chain, which is usually not what you want.

A useful shortcut:

• ser = what something is
• estar = how something is

A is the feminine singular definite article, meaning the.

So:

• a corrente = the chain

Portuguese nouns usually take an article more often than in English, so using a here is completely normal.

Because corrente is a feminine noun in Portuguese, so it takes:

• the feminine article a
• a feminine adjective, if needed

That is why you get:

• a corrente
• suja and not sujo

Grammatical gender in Portuguese is a property of the noun, and it does not always match natural gender or any obvious logic in English. It is something you often just need to learn with each noun.

Adjectives in Portuguese usually agree with the noun in gender and number.

Since corrente is feminine singular, the adjective must also be feminine singular:

• masculine singular: sujo
• feminine singular: suja
• masculine plural: sujos
• feminine plural: sujas

So:

• o fio está sujo
• a corrente está suja

No. Corrente can have several meanings depending on context, such as:

• chain
• current (for example water current or electrical current)
• sometimes stream or flow
• in some contexts, even common / current as an adjective

So the exact meaning depends on the situation. In your sentence, if the meaning shown is The chain is dirty, then that is the intended meaning here.

A rough European Portuguese pronunciation is:

uh koo-REN-tuh shtah SOO-zhuh

A few important points:

• a often sounds like a weak uh
• corrente has stress on ren
• está often sounds closer to shtá in European Portuguese
• j in suja sounds like the s in measure

This is only an approximation for English speakers, but it helps you get close.

Normally, no. In standard Portuguese, you would usually keep the article and say A corrente está suja.

Leaving out the article here sounds incomplete or unnatural in ordinary speech, unless you are speaking in a very special context such as notes, labels, headlines, or very telegraphic language.

Yes, but A corrente está suja is the most neutral and natural order.

You might also hear:

• Está suja, a corrente — more marked, often for emphasis
• Suja está a corrente — very marked or literary

For normal conversation, stick with:

• A corrente está suja

The plural is:

As correntes estão sujas.

Here everything changes to plural:

• a → as
• corrente → correntes
• está → estão
• suja → sujas

So Portuguese keeps agreement across the whole sentence.

Yes, both are possible, but they differ in strength.

• suja = dirty
• imunda = filthy, very dirty

So suja is the normal everyday word.
Imunda is stronger and more emphatic.

For most basic situations, suja is the safest and most common choice.