O líder verificou a bicicleta.

Because o is the masculine singular definite article, meaning the.

So O líder means the leader.

In Portuguese, articles are used very regularly, often more regularly than in English. You usually cannot just say líder here if you mean the leader in a normal complete sentence.

Líder can refer to either a man or a woman. The article tells you the gender in a specific sentence:

• o líder = the male leader
• a líder = the female leader

So in your sentence, O líder verificou a bicicleta, the leader is understood as male because of o.

The accent mark shows where the stress goes: LÍ-der.

Without the accent, the word would not follow normal Portuguese stress expectations. The accent helps you pronounce it correctly.

So the stressed syllable is the first one:

• líder

Verificou is the 3rd person singular of the verb verificar in the pretérito perfeito simples.

That means it describes a completed action in the past:

• verificou = he/she checked, he/she verified, he/she inspected

In this sentence, it means the action is finished: the leader checked the bicycle.

Not always.

Although verificar is related to English verify, in Portuguese it is often used in a broader everyday sense, closer to:

• check
• inspect
• look over
• confirm

So in verificou a bicicleta, a very natural English translation is often checked the bicycle, not only verified the bicycle.

Because bicicleta is a feminine singular noun.

So it takes the feminine singular article a:

• a bicicleta = the bicycle

This is just grammatical gender. It does not mean the bicycle is biologically female; it simply means the noun belongs to the feminine grammatical class.

Normally, no, not in this sentence.

If you mean the bicycle, you use a bicicleta.

If you mean a bicycle, you would normally say:

• uma bicicleta

So the article helps show whether you mean a specific bicycle or just any bicycle.

It is not written, because Portuguese often leaves out subject pronouns when the verb form already shows the person.

Here, verificou tells you the subject is he/she/it in the past.

So Portuguese can simply say:

• O líder verificou a bicicleta.

If you wanted, you could also say:

• Ele verificou a bicicleta.

But ele is not necessary unless you want emphasis, contrast, or clarity.

It follows the normal Portuguese pattern:

• Subject + Verb + Direct Object

So here:

• O líder = subject
• verificou = verb
• a bicicleta = direct object

This is the same basic order as in English:

• The leader checked the bicycle.

In European Portuguese, verificou is pronounced with the stress on the last syllable.

A rough guide is:

• vuh-ree-fee-KOH

More exactly, the final -ou in European Portuguese is often pronounced more like -o than like a strong English ow sound.

So the stress is:

• veri-fi-COU

A rough pronunciation guide is:

• u LEE-dêr vuh-ree-fee-KOH uh bee-see-KLEH-tuh

A few useful points:

• O often sounds like u in European Portuguese.
• líder is stressed on the first syllable.
• verificou is stressed on the last syllable.
• a is often a very reduced vowel in European Portuguese.
• bicicleta is stressed on kle: bi-ci-CLE-ta

If you want a more IPA-style version, it is approximately:

• [u ˈliðɛɾ vɨɾifiˈko ɐ bisiˈklɛtɐ]

Yes.

By itself, verificou can mean:

• he checked
• she checked
• it checked

The verb form does not show gender.

In your sentence, gender comes from o líder, which shows that the subject is masculine. If it were a líder, then it would mean the female leader checked the bicycle.