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"Quien" is a form of "quien", a pronoun which is often translated as "who". "Aquel" is an adjective which is often translated as "that". Learn more about the difference between "aquel" and "quien" below.
aquel(
ah
-
kehl
)An adjective is a word that describes a noun (e.g., the big dog).
a. that
Me gusta mucho aquella casa que hay en lo alto de la colina.I really like that house on top of the hill.
Aquel coche estacionado allá es mío.That car parked over there is mine.
quien(
kyehn
)A pronoun is a word that stands in for a noun (e.g., she).
1. (relative)
2. (indefinite)
a. anyone
Puedes elegir a quien quieras siempre y cuando levanten la mano.You can choose anyone you like as long as they raise their hand.