For the act of lying (telling an untruth):
* mentir: This is the most common word for "lie."
* falar mentira: This is a more literal translation, meaning "to speak a lie."
For the position of lying down:
* deitar-se: This means "to lie down."
For a lie as a falsehood:
* mentira: This is the noun form of "lie," meaning "lie" as a falsehood.
Example sentences:
* Ele mentiu sobre sua idade. (He lied about his age.)
* Ela falou mentira para ele. (She told a lie to him.)
* Estou deitado na cama. (I am lying down on the bed.)
* Não acredito na mentira que ele contou. (I don't believe the lie he told.)
It's important to consider the context to choose the correct word for "lie" in Portuguese.