How the word "quién" is translated into English
¿Quién es?
[¿ˈkjen ˈes?]
Who is it?
¿Quién quiere más pastel?
[¿ˈkjeŋ ˈkjeɾe ˈmas pasˈtel?]
Who wants more cake?
No sé quién es ese chico.
[no ˈse ˈkjen ˈes ˈese ˈʧiko.]
I don't know who that boy is.
"quién" is in the lesson "Pronouns" (Level 30), along with 17 other useful words. LinDuo has 180 topic lessons like this one, 2,369 words in total. Every word has an illustration, a transcription and pronunciation in a female and a male voice. Just 10–15 minutes a day is enough to learn them all. Free, and works offline.