É mentira.

Use É mentira when you hear something you know is false. You can say it right after someone tells you something unbelievable. For example, if your friend claims they met a celebrity, and you know they didn't, you'd say, É mentira!. It works in almost any conversation where truth is in question. Just remember to deliver it with the right tone – a wink can make it friendly, a stern look makes it serious. Don't be surprised if Brazilians use it a lot when watching sports or discussing politics!

This phrase is generally informal. You'll hear it a lot among friends, family, and in casual settings. It's not something you'd typically use in a very formal business meeting or a legal document. Think texting, chatting with colleagues you know well, or commenting on a social media post. Using it in a formal context might sound a bit blunt or even rude, so be mindful of your audience. It's like wearing flip-flops to a wedding – usually not the best choice!

• Texting: 'Meu irmão disse que limpou o quarto todo. É mentira!' (My brother said he cleaned the whole room. It's a lie!)
• At a café: 'Você acredita que ele ganhou na loteria? É mentira, ele tá brincando.' (Can you believe he won the lottery? It's a lie, he's joking.)
• Watching TV: 'O personagem principal sobreviveu? No meu livro, é mentira!' (The main character survived? In my book, it's a lie!)
• Social Media: Someone posts a wild story. You comment: É mentira!

Use É mentira when you want to directly challenge a statement you believe is false. It's perfect for moments of surprise or disbelief. If someone tells a tall tale, you can use it to playfully call them out. It's also useful when you know the factual inaccuracy of something being discussed. For instance, if a friend claims É mentira that it's raining, and you can see the downpour outside, you've got your phrase! It's your go-to for debunking myths or exaggerations in everyday chat.

Avoid É mentira in highly formal situations like job interviews, serious negotiations, or when speaking to authority figures you don't know well. It can sound accusatory and unprofessional. Also, if you're not 100% sure something is a lie, it might be safer to phrase your doubt differently, like Será? (Really?) or Não acredito. (I don't believe it.). Using it when you might be wrong could cause unnecessary conflict. It’s not the phrase to use if you want to tiptoe around someone’s feelings.

• ✗ É verdade mentira. → ✓ É mentira. (Mixing verdade - truth - with mentira - lie - doesn't make sense here!)
• ✗ Isso é mentira. → ✓ É mentira. (While Isso é mentira means 'That is a lie', É mentira is the more common, punchier, and natural idiomatic expression in many casual contexts.)
• ✗ Mentira é. → ✓ É mentira. (Incorrect word order. Portuguese word order matters, folks!)

• Que mentira!: Similar to É mentira, but perhaps a bit more emphatic. 'What a lie!'
• Isso é mentira!: Also means 'That's a lie!' It's a bit more explicit about referring to 'that'.
• Não é verdade.: Means 'It's not true.' A slightly softer way to deny something.
• Mentira!: Just the word 'Lie!' – very informal and often used as an exclamation.
• Regional: In some places, you might hear variations, but É mentira is universally understood across Brazil and Portugal.

• Is it always aggressive? Not at all! Tone is key. It can be playful or serious.
• Can I use it in writing? Yes, in informal writing like texts or social media comments. Avoid formal emails.
• What if I'm wrong? Oops! It might cause embarrassment. Better to use softer phrases if unsure.
• Is it common? Super common! You'll hear it constantly in casual Portuguese conversation.