Obrigado pela companhia.

In Portuguese, obrigado/obrigada changes according to the gender of the speaker, not the listener.

• A man says obrigado
• A woman says obrigada

So if a woman is saying this sentence, she would usually say Obrigada pela companhia.

Teaching materials sometimes write obrigado(a) to show both possibilities, but in real speech you choose just one form.

Yes. It can become plural.

• obrigados = used by a group of men, or a mixed group
• obrigadas = used by a group of women

So a group could say:

• Obrigados pela companhia
• Obrigadas pela companhia

Again, it agrees with the people who are speaking.

Pela is a contraction of por + a.

• por = for
• a = the

Because companhia is a feminine noun, a is the article used with it. So:

• por + a companhia → pela companhia

This kind of contraction is extremely common in Portuguese.

After obrigado/obrigada, Portuguese normally uses por to say what you are thanking someone for.

For example:

• Obrigado por tudo
• Obrigada pela ajuda
• Obrigado pelo presente

Using para here would not sound natural in standard Portuguese. In this pattern, por is the normal choice.

No. Here companhia means company in the sense of someone's presence or companionship.

So in this sentence it means something like:

• being with someone
• keeping someone company
• spending time together

The same word can also mean a business or company in other contexts, but not here.

Yes, that is correct.

• Obrigado pela companhia sounds very natural and idiomatic.
• Obrigado por sua companhia is also correct, but a bit more explicit.

Using sua can sound slightly more formal, polite, or deliberate depending on the situation. In everyday speech, pela companhia is often the more natural choice.

It is fairly neutral. You can use it in many situations:

• with friends
• with family
• with guests
• with coworkers
• after a visit or shared activity

It does not sound slangy, but it is also not overly formal. If you want to sound warmer, you can say Muito obrigado pela companhia or Muito obrigada pela companhia.

You use it when you want to thank someone for spending time with you or for being present.

Typical situations include:

• at the end of a visit
• after a meal together
• after a conversation
• after an event
• when someone accompanied you somewhere

It focuses on the person's presence, not on a physical gift or favor.

A rough English-friendly pronunciation is kohm-pahn-YEE-ah.

A few points:

• the nh sounds like ny in canyon
• the stress is on -ni-
• the final a is clearly pronounced

So it sounds approximately like:

• com-pa-nhi-a

In Brazilian Portuguese, the full sentence is roughly:

• obree-GAH-doo PEH-lah kohm-pahn-YEE-ah
  or
• obree-GAH-dah PEH-lah kohm-pahn-YEE-ah

depending on the speaker's gender.

Yes. That is very common.

• Muito obrigado pela companhia
• Muito obrigada pela companhia

Adding muito makes it sound more heartfelt: thank you very much for the company/companionship.

You could also say Obrigadão pela companhia in very informal Brazilian Portuguese, but muito obrigado/a is the safer and more widely usable choice.