Why? – ¿por qué?
(Pronounced pohr-keh)
To remember that why is pronounced pohr-keh (por qué) in Spanish, use the following mnemonic:
Why did his trousers no longer fit? He'd got porky (por qué) because he'd been stuffing his face too much.

Examples of por qué (why) in a sentence
¿Por qué no vienes a la fiesta esta noche?
(Why aren't you coming to the party tonight?)
No entiendo por qué llegaste tan tarde.
(I don't understand why you arrived so late.)
¿Por qué estudias español todos los días?
(Why do you study Spanish every day?)