O mamão está maduro agora, mas ontem o abacaxi ainda estava verde.

In Portuguese, it is very common to use the definite article with nouns, even when English would often leave it out.

So Portuguese says:

• O mamão está maduro agora
• O abacaxi ainda estava verde

In natural English, we might say:

• Papaya is ripe now
• The papaya is ripe now

Both can work depending on context, but Portuguese often prefers the article when talking about a specific fruit or a fruit understood from the situation.

Here, o means the and matches the gender and number of the noun:

• o mamão = the papaya
• o abacaxi = the pineapple

Both nouns are masculine singular, so they take o.

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

Ripeness is a condition that changes, so Portuguese uses estar:

• O mamão está maduro. = The papaya is ripe.

If you used ser here, it would sound unnatural because being ripe is not an essential, permanent quality of the fruit.

The same logic applies to verde in this sentence:

• o abacaxi ainda estava verde

Here verde means unripe, which is also a temporary state, so estar is the correct verb.

They are two forms of the verb estar:

• está = is / is being, present tense
• estava = was, imperfect past

So:

• O mamão está maduro agora = The papaya is ripe now.
• ontem o abacaxi ainda estava verde = yesterday the pineapple was still green/unripe.

The sentence contrasts the present and the past:

• agora goes with está
• ontem goes with estava

The imperfect estava is especially natural here because it describes a state in the past, not a completed action.

This is a very common learner question.

Portuguese often uses the imperfect (estava) to describe an ongoing state or condition in the past. Since being unripe is a state, estava fits well:

• Ontem o abacaxi ainda estava verde.
  = Yesterday the pineapple was still unripe.

If you said esteve, that would use the preterite, which usually presents the situation more as a completed event. That is less natural in this context.

A good shortcut is:

• estava = was, in a descriptive/background sense
• esteve = was, but more event-like or bounded

Here, the sentence is simply describing the pineapple’s condition yesterday, so estava is the normal choice.

In Portuguese, just like in English, color words can sometimes describe condition rather than literal color.

With fruit:

• maduro = ripe
• verde = unripe / not ripe yet

So in this sentence, verde does not only mean the color green. It means the pineapple had not ripened yet.

This is very common:

• A banana está verde. = The banana is unripe.
• O tomate ainda está verde. = The tomato is still unripe.

Of course, verde can also just mean the color green in other contexts.

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

Both mamão and abacaxi are masculine singular nouns, so the adjective is also masculine singular:

• o mamão maduro
• o abacaxi verde

For maduro, the forms would be:

• maduro = masculine singular
• madura = feminine singular
• maduros = masculine plural
• maduras = feminine plural

Example with a feminine noun:

• A banana está madura.

Notice that verde does not change in the singular masculine/feminine form:

• o abacaxi verde
• a banana verde

Ainda means still here.

So:

• ontem o abacaxi ainda estava verde = yesterday the pineapple was still unripe

It shows that the state continued up to that point. The pineapple had not ripened yet.

Compare:

• O abacaxi estava verde. = The pineapple was unripe.
• O abacaxi ainda estava verde. = The pineapple was still unripe.

The version with ainda emphasizes continuation and often suggests a later change may happen.

Yes, Portuguese word order is fairly flexible, especially with time expressions like agora and ontem.

The sentence as given is very natural:

• O mamão está maduro agora, mas ontem o abacaxi ainda estava verde.

But these are also possible:

• Agora, o mamão está maduro...
• O mamão agora está maduro...
• Ontem, o abacaxi ainda estava verde.

The original order sounds smooth and conversational. Portuguese often places time expressions where they sound most natural or where the speaker wants emphasis.

So the placement is not a strict rule here; it is a style and emphasis choice.

Mas means but.

It connects two contrasting ideas:

• O mamão está maduro agora
• mas ontem o abacaxi ainda estava verde

The contrast is not necessarily between papaya and pineapple alone, but also between:

• now vs yesterday
• ripe vs still unripe

So mas helps create a clear comparison.

A simple approximate guide for an English speaker:

• mamão ≈ mah-MOWN
  The ão sound is nasal, which English does not really have. Try saying ow while letting some air go through your nose.

• abacaxi ≈ ah-bah-kah-SHEE
  In Brazilian Portuguese, xi often sounds like shee.

• está ≈ eh-STAH
  Stress is on the last syllable.

A few key pronunciation points:

• ã / ão are nasal sounds.
• Final stressed á is an open ah sound.
• In Brazil, x in abacaxi sounds like sh.

Portuguese can use pronouns, but repeating the nouns is often clearer and more natural, especially when comparing two different things.

Here the sentence contrasts two fruits:

• O mamão...
• o abacaxi...

If you replaced one with a pronoun, it might be less clear or less balanced. For example:

• O mamão está maduro agora, mas ontem ele ainda estava verde.

Here ele would most likely refer to o mamão, not o abacaxi, so it changes the meaning or creates ambiguity.

Using both nouns makes the contrast very clear.

Yes, that is grammatically correct, but it loses some nuance.

Original:

• O mamão está maduro agora, mas ontem o abacaxi ainda estava verde.

This gives extra information:

• agora = now
• ainda = still

Without them:

• O mamão está maduro, mas ontem o abacaxi estava verde.

This is simpler and still correct, but:

• agora strengthens the contrast with ontem
• ainda suggests the pineapple had not ripened yet at that past moment

So the original version is richer and more precise.