A bomba de bicicleta funciona bem.

A means the, while uma means a/an.

So:

• a bomba = the pump
• uma bomba = a pump

In this sentence, a is used because the speaker is referring to a specific bicycle pump, or to the bicycle pump in a general, identifiable sense.

In Portuguese, nouns have grammatical gender. Bomba is a feminine noun, so it takes the feminine singular article a.

That is why you get:

• a bomba
• not o bomba

This is something you usually just have to learn with the noun.

Here, de bicicleta means for bicycles or bicycle- in English.

So bomba de bicicleta is literally:

• pump of bicycle

but in natural English we say:

• bicycle pump

Portuguese often uses de + noun where English uses one noun to describe another.

Compare:

• bomba de bicicleta = bicycle pump
• sapatos de couro = leather shoes
• garrafa de água = water bottle

Good question. There is an important difference:

• de bicicleta = bicycle pump / pump for bicycles
• da bicicleta = the pump of the bicycle

In your sentence, de bicicleta describes the type of pump. It is a pump used for bicycles.

If you said a bomba da bicicleta, it would usually mean a specific pump belonging to a particular bicycle, which is less likely in this context.

Funciona is the 3rd person singular form of the verb funcionar (to function / to work).

The subject is a bomba de bicicleta, which is singular, so the verb must also be singular:

• a bomba ... funciona = the pump ... works

If the subject were plural, the verb would change:

• as bombas de bicicleta funcionam bem = the bicycle pumps work well

In Portuguese, funcionar is a very common way to say that a machine, device, or system works.

So:

• A bomba funciona. = The pump works.

Portuguese can also use trabalhar, but that usually means to work in the sense of doing a job or being employed, not for machines like this.

Bem means well.

So:

• funciona bem = works well

It is an adverb modifying the verb funciona.

Other examples:

• Ele fala bem português. = He speaks Portuguese well.
• O carro anda bem. = The car runs well.

You might hear similar things in some contexts, but it is not the best equivalent here.

• funciona bem focuses on performance: it works properly.
• está boa can mean it is in good condition, okay, or fine, but it is less direct for saying a device is functioning well.

For a machine or tool, funciona bem is the most natural choice if you mean it operates properly.

No. Bomba can mean different things depending on context.

Common meanings include:

• pump
• bomb

In a bomba de bicicleta, the meaning is clearly pump because of de bicicleta.

Context usually makes the meaning obvious.

Usually, in a normal sentence like this, you would keep it:

• A bomba de bicicleta funciona bem.

If you drop the article and say Bomba de bicicleta funciona bem, it sounds unnatural as a standard sentence.

Portuguese uses articles more often than English, so English speakers often need to remember not to leave them out.

A rough European Portuguese pronunciation is:

a BOM-ba d(i) bici-CLE-ta fun-SYO-na beng

A few helpful points:

• de is often reduced, sounding closer to d(i) in connected speech.
• bicicleta in European Portuguese often has a weaker unstressed vowel pattern than an English speaker might expect.
• bem in European Portuguese has a nasal sound at the end.

You do not need perfect pronunciation immediately, but it helps to notice that European Portuguese often reduces unstressed vowels more than Brazilian Portuguese.

The plural would be:

As bombas de bicicleta funcionam bem.

Changes:

• a → as
• bomba → bombas
• funciona → funcionam

de bicicleta stays the same here because it is just describing the type of pump.