Eu disse tchau.

Disse is the first-person singular preterite form of dizer, which means to say.

So:

• dizer = to say
• eu disse = I said

This is an irregular verb, so you cannot guess disse just by taking the infinitive and adding a regular ending.

Disse is in the pretérito perfeito (the simple past / preterite).

It refers to a completed action in the past:

• Eu disse tchau. = I said bye.

It does not mean I was saying bye. For that kind of ongoing past idea, Portuguese would use a different structure.

Yes, you often can.

Portuguese frequently drops subject pronouns when the verb already makes the subject clear. Since disse clearly matches eu in this context, Disse tchau can work.

Including eu can:

• add emphasis
• add contrast
• make the subject extra clear

So both are possible:

• Eu disse tchau.
• Disse tchau.

In normal writing, both are possible, but quotation marks are usually not necessary here.

Portuguese often treats greetings and farewells like olá, oi, and tchau as words you can directly say without needing quotation marks:

• Ela disse oi.
• Ele falou tchau.

If you want to emphasize the exact word spoken, you can use quotation marks:

• Eu disse “tchau”.

But in everyday writing, leaving them out is very common.

Yes, Eu falei tchau is also possible in Brazilian Portuguese.

There is some overlap between dizer and falar in informal speech:

• dizer = to say
• falar = to speak / to say

So both can work in sentences like this.

However, dizer is often the more direct match for English say, especially when referring to the actual words spoken.

So:

• Eu disse tchau. = very natural
• Eu falei tchau. = also natural in many contexts

Tchau is generally informal to neutral and extremely common in Brazil.

It is the normal everyday way to say bye or goodbye in casual speech.

Compared with adeus:

• tchau = common, everyday, casual
• adeus = more dramatic, less common in everyday Brazilian speech, sometimes sounds more final

So in most ordinary situations, tchau is the natural choice.

A rough Brazilian Portuguese pronunciation is:

• Eu ≈ eh-oo / yoo-like, depending on accent
• disse ≈ JEE-see or DJEE-see in many Brazilian accents
• tchau ≈ chow

A rough full approximation: eh-oo JEE-see chow

A few notes:

• d before i often sounds like j in many Brazilian accents
• ss in disse sounds like s
• tchau rhymes closely with English cow, but starts with a ch sound

Yes. That is normal.

Here tchau is functioning like the word being said, similar to how English works in:

• I said bye.
• She said hello.

So Portuguese naturally allows:

• dizer oi
• dizer olá
• dizer tchau

No article is needed.

This is the most normal word order:

• Eu = subject
• disse = verb
• tchau = what was said

So Eu disse tchau is the standard order.

Other orders are possible only in special contexts, but they are less neutral. For a learner, it is best to stick with:

• Eu disse tchau.

Not exactly.

• Eu disse tchau = I said bye
• Eu dei tchau = I waved goodbye / I said goodbye

Dar tchau is a very common Brazilian expression and often suggests the act of saying or gesturing goodbye, especially waving.

So:

• Eu disse tchau focuses on the words
• Eu dei tchau often focuses on the farewell action

No. In natural English, we say I said goodbye, not I told goodbye.

That helps explain the Portuguese too:

• dizer usually matches say
• contar or dizer a alguém can be closer to tell in other contexts

So Eu disse tchau is specifically like I said bye / I said goodbye.

Yes. You can add the person with para/pra:

• Eu disse tchau para ela. = I said bye to her.
• Eu disse tchau pra ele. = I said bye to him.

In speech, pra is very common and natural in Brazil.

Yes, it is grammatical and natural, especially if you are reporting what you said.

For example:

• Antes de sair, eu disse tchau. = Before leaving, I said bye.

That said, depending on context, Brazilians might also say:

• Eu falei tchau.
• Eu dei tchau.

All three are possible, but Eu disse tchau is perfectly good Portuguese.