A luta começou.

A is the definite article, meaning the. So a luta is the fight/the struggle.

If you said uma luta, that would mean a fight/a struggle in a more indefinite sense.

• a luta = the fight
• uma luta = a fight

Because luta is a feminine noun in Portuguese.

Singular definite articles:

• o for masculine nouns
• a for feminine nouns

So:

• o livro = the book
• a luta = the fight

This gender is grammatical, so it has to match the noun.

Luta can mean fight, struggle, or combat, depending on context.

For example:

• in sports or physical conflict, it can mean fight
• in a figurative sense, it can mean struggle

In A luta começou., the exact nuance depends on the situation, but grammatically it is simply the noun luta.

Começou is the preterite form of the verb começar.

The preterite in Portuguese is commonly used for a completed action in the past. Here, it marks the moment when the action began:

• começar = to begin / to start
• começou = began / started

So this sentence presents the beginning of the fight as a finished event in the past.

The accent in começou is important both for pronunciation and spelling.

It shows the stressed syllable and helps distinguish the correct verb form:

• começou = he/she/it started or you started (formal você)
• comecou is not correct spelling

Also, the ç in começou is necessary:

• ç makes an s sound before a, o, or u
• so começou sounds roughly like ko-me-SOH

Without the cedilla:

• c before o would sound like k, which would be wrong

In this sentence, the subject is A luta.

So começou means started/began, and the fight is what started.

It does not mean that a person started something. It means the fight itself began.

Structure:

• A luta = subject
• começou = verb

So the sentence is literally:

• The fight began

Because Portuguese, like English, often prefers a simple active-style structure when something begins on its own:

• A luta começou. = The fight began.

You could make other sentences if you want to focus on who initiated it, but this sentence simply states that the event started. It does not say who caused it.

Yes. Começou a luta is possible and natural.

Both are grammatical:

• A luta começou.
• Começou a luta.

The difference is mostly one of focus or style:

• A luta começou. sounds more neutral, with the fight as the topic
• Começou a luta. puts slightly more focus on the fact that it started

For a learner, A luta começou. is the most straightforward structure to remember.

A simple approximation is:

ah LOO-tah ko-me-SOH

A few pronunciation notes:

• A = a short ah
• luta = LOO-tah
• começou = ko-me-SOH
• the final stress is on çou

In natural Brazilian speech, the final u sound in começou can be light.

Not only that. Começou can also be used with você.

So it can mean:

• he started
• she started
• it started
• you started (when you = você)

But in A luta começou, the subject is a luta, so here it clearly means it started / began.

The infinitive is começar, meaning to begin or to start.

A few forms:

• começar = to start
• começa = starts / is starting
• começou = started
• começava = used to start / was starting
• começará = will start

So começou is one conjugated form of começar.

In normal Portuguese, you would usually say A luta começou.

Leaving out the article and saying Luta começou sounds unnatural in most ordinary contexts.

Portuguese uses definite articles more often than English does, especially with nouns that are specific and known in the context. So a luta is the natural choice here.