O parceiro chegou cedo.

O is the masculine singular definite article, equivalent to the in English.

So:

• o parceiro = the partner
• um parceiro = a partner

Portuguese uses articles very often, sometimes more often than English does, so seeing o/a/os/as before a noun is very normal.

Because parceiro is the masculine form of the noun.

• o parceiro = the male partner / partner (masculine)
• a parceira = the female partner / partner (feminine)

In Portuguese, nouns often have grammatical gender, and the article has to match:

• o parceiro
• a parceira

If you were talking about a woman, the sentence would be A parceira chegou cedo.

Chegou is the preterite form of chegar and means arrived.

It is:

• 3rd person singular
• used for he/she/it arrived, or you arrived in formal você speech

So:

• eu cheguei = I arrived
• você/ele/ela chegou = you/he/she arrived

In this sentence, chegou matches o parceiro.

Chegou and chegava are both past forms, but they are used differently.

• chegou = a completed event, arrived
• chegava = ongoing/repeated/background action, often was arriving, used to arrive, or something similar depending on context

Here, O parceiro chegou cedo presents the arrival as a finished event: the partner arrived early.

If you said O parceiro chegava cedo, it would usually mean something more like The partner used to arrive early or was arriving early, depending on context.

Cedo is an adverb meaning early.

It modifies the verb chegou, telling us how/when the person arrived.

So:

• chegou cedo = arrived early

Cedo does not change form for gender or number. It stays cedo.

Portuguese often leaves out subject pronouns when the subject is already clear.

In this sentence, the subject is explicitly named: O parceiro. Because of that, there is no need to add ele.

Portuguese also frequently omits pronouns even when the subject is not stated as a noun, because the verb ending often gives enough information:

• Cheguei cedo. = I arrived early.
• Chegou cedo. = He/she/you arrived early.

Here, the subject is already present, so O parceiro chegou cedo is complete and natural.

Yes. Parceiro can mean different things depending on context.

It can refer to:

• a romantic partner
• a business partner
• a teammate
• a companion
• in some contexts, even something like buddy or mate

So the exact meaning depends on the situation. The grammar of the sentence stays the same.

This is the most neutral and common word order:

• subject + verb + adverb
• O parceiro chegou cedo

Portuguese can sometimes change word order for style, emphasis, or specific contexts, but this version is the standard one for a basic statement.

For a learner, O parceiro chegou cedo is the safest and most natural pattern to use.

In Brazilian Portuguese, chegou is approximately pronounced like sheh-GOH.

A few points:

• ch in Brazilian Portuguese usually sounds like sh
• the stress is on the last syllable: che-GOU
• the ending ou is usually pronounced like a clear oh sound in normal Brazilian speech

So a rough English approximation is:

• chegou ≈ sheh-GOH

This is only an approximation, but it helps many beginners.

A rough approximation is par-SAY-roh, with the stress on cei.

More specifically:

• par sounds roughly like par
• cei sounds somewhat like say
• ro at the end is lighter than English row, often closer to roh

So:

• parceiro ≈ par-SAY-roh

Again, this is just an English-friendly approximation.

That is the normal position for many adverbs in Portuguese, especially in simple sentences.

• chegou cedo = arrived early

Placing cedo after the verb sounds natural and straightforward. Portuguese often puts adverbs like this after the verb, although other positions are sometimes possible for emphasis or style.

For a beginner, it is best to learn:

• Ele chegou cedo.
• O parceiro chegou cedo.

Possibly, yes, depending on context.

Because parceiro can refer to different kinds of partners, in the right situation it could mean something like:

• partner
• boyfriend
• companion

But you should not assume it is always romantic. Without more context, partner is the safest broad translation.