A colheita começa amanhã.

A is the feminine singular definite article, meaning the.

It is used because colheita is a feminine singular noun. In Portuguese, nouns usually need an article more often than in English, so A colheita is a very natural way to say the harvest.

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

So here:

• a colheita = the harvest

Yes, colheita is feminine.

One clue is that it ends in -a, which often signals a feminine noun in Portuguese, though not always. Because it is feminine, it takes the article a.

Examples:

• a colheita
• a vindima
• a fruta

You usually need to learn the gender together with the noun.

Because começa is the conjugated verb, while começar is the infinitive.

The subject is a colheita, which is third person singular, so the verb must match it:

Present tense of começar:

• eu começo
• tu começas
• ele/ela/você começa
• nós começamos
• vós começais
• eles/elas/vocês começam

So:

• A colheita começa amanhã.

Not:

• A colheita começar amanhã. → ungrammatical in this sentence

In Portuguese, just like in English, the present tense can be used for a future event when there is a clear time expression.

Here, amanhã makes the future meaning obvious, so começa naturally means starts tomorrow.

This is very common:

• O filme começa às oito.
• Partimos amanhã.
• As aulas começam em setembro.

If you want, you can also use a future form, but the present is completely normal here.

Yes. A colheita vai começar amanhã is also correct.

That structure uses ir + infinitive, which is a very common way to talk about the future:

• vai começar = is going to start / will start

Difference in feel:

• A colheita começa amanhã = simple, natural, scheduled fact
• A colheita vai começar amanhã = also natural, slightly more explicitly future

Both are good.

Yes. Portuguese allows some flexibility in word order.

All of these are possible:

• A colheita começa amanhã.
• Amanhã, a colheita começa.

The first is the most neutral.
The second puts more focus on tomorrow.

This kind of fronting is very common when the speaker wants to highlight the time.

In European Portuguese, colheita is pronounced approximately like:

culh-AI-ta
IPA: /kuˈʎɐjtɐ/

A few important points:

• lh is a special sound, like the lli in some pronunciations of million, or like Spanish ll in some accents
• the stressed part is hei
• the final a in European Portuguese is usually reduced, not a full open ah

So it does not sound like each letter separately.

The ç is called cedilha. It makes the c sound like s before a, o, or u.

So:

• começa is pronounced with an s sound
• without the cedilla, comeca would suggest a k sound, which is wrong

Compare:

• ca = k sound
• ça = s sound

So começa sounds roughly like ku-MEH-sa in European Portuguese.

In European Portuguese, amanhã is approximately:

a-ma-NYÃ
IPA: /ɐmɐˈɲɐ̃/

Important parts:

• nh sounds like Spanish ñ or the ny in canyon
• ã is nasal, so the sound comes partly through the nose
• the stress is on the last syllable

For English speakers, the hardest part is usually the nasal ending. Try not to pronounce it as a plain a.

Because the subject is already stated: A colheita.

Portuguese does not need an extra subject pronoun when the subject noun is present.

So:

• A colheita começa amanhã. = correct
• A colheita ela começa amanhã. = usually unnecessary and unnatural in standard usage

You only add a pronoun for special emphasis or contrast, and even then it depends on the structure.

Usually, yes: it refers to the harvesting or the harvest itself.

Depending on context, it can mean:

• the act of harvesting
• the harvest season
• the harvested produce

It can also be used figuratively in some contexts, like reaping results, but the agricultural meaning is the basic one.

Related words:

• colher = to harvest / to collect
• colheita = harvest
• vindima = grape harvest

The sentence works in both European Portuguese and Brazilian Portuguese.

Both would understand and use:

• A colheita começa amanhã.

The main differences would be in pronunciation, not grammar.

For example:

• European Portuguese tends to reduce unstressed vowels more
• Brazilian Portuguese tends to pronounce vowels more clearly

But the sentence itself is standard in both varieties.