A argila endureceu durante a noite.

A is the feminine singular definite article, meaning the.

So a argila = the clay.

In Portuguese, nouns are often used with an article more often than in English. That can happen even when English might simply say clay. Here, argila is a feminine noun, so it takes a.

• o = masculine singular
• a = feminine singular
• os = masculine plural
• as = feminine plural

Because argila is feminine singular, a is the correct article.

You usually learn the gender together with the noun: a argila, not just argila.

There are patterns that help:

• many nouns ending in -a are feminine
• many nouns ending in -o are masculine

So argila being feminine fits a very common pattern. But it is still best to memorize nouns with their article, because there are exceptions in Portuguese.

Endureceu is in the pretérito perfeito do indicativo, which is the normal simple past tense in Portuguese.

Here it means that the hardening happened as a completed event in the past:

• A argila endureceu. = The clay hardened.

This tense is often used for actions that are seen as completed.

The infinitive is endurecer, meaning to harden or to become hard.

Endureceu is the ele/ela/você form of the simple past (pretérito perfeito) of endurecer.

A very useful pattern:

• many -er verbs in this tense have -eu for he/she/it
• for example:
  • comeu = ate
  • bebeu = drank
  • endureceu = hardened / became hard

So:

• eu endureci
• tu endureceste
• ele/ela/você endureceu

It can mean either, depending on how you translate it into natural English.

In this sentence, endureceu is an intransitive use: the clay itself changed state.

So the idea is:

• the clay hardened
• or the clay became hard

Both are good English translations.

If you wanted a more clearly transitive meaning, like something hardened the clay, Portuguese would normally need a different structure, for example with an object.

Durante means during, and a noite means the night.

So:

• durante a noite = during the night / overnight

In this sentence, it tells you when the hardening happened.

It suggests that the process took place over the course of the night, and by the next morning the clay had hardened.

Not usually if you want exactly the same meaning.

Durante a noite is better here because it emphasizes that the process happened over the period of the night.

De noite more often means:

• at night
• night-time
• something habitual or general

For example:

• Trabalho de noite. = I work at night.

But in A argila endureceu durante a noite, the focus is on a completed process happening over that stretch of time, so durante a noite fits better.

Because this is a very neutral Portuguese sentence:

• A argila = subject
• endureceu = verb
• durante a noite = time expression

So the structure is:

Subject + Verb + Time expression

That is very common in both Portuguese and English. Portuguese word order can be more flexible than English, but in a plain statement like this, this order is the most natural.

In European Portuguese, it is approximately:

A argila endureceu durante a noite.
/ɐ ɐɾˈʒilɐ ĩduɾɨˈsew duˈɾɐ̃tɨ ɐ ˈnojtɨ/

A few helpful pronunciation points:

• argila: the gi sounds like the s in measure
• endureceu: the final -eu sounds roughly like eh-oo said quickly together
• noite: sounds roughly like NOYT(ə) in European Portuguese, with a very light final vowel

Also, in European Portuguese, unstressed vowels are often reduced, so some vowels sound less clear than an English speaker might expect.

Yes. Argila is the normal word for clay as a material.

For example:

• uma peça de argila = a clay piece
• solo argiloso = clay soil / clayey soil

So in this sentence, argila is exactly the standard word you would expect.

Most naturally, it refers to a specific clay mass or piece of clay in the context.

Because it uses the definite article a, the most straightforward reading is the clay.

However, Portuguese sometimes uses definite articles in ways that are a bit broader than English does, so context matters. Still, if you saw this sentence by itself, you would normally understand it as referring to some particular clay that has already been mentioned or is understood from the situation.