QUICK ANSWER
"Who" is a form of "who", a pronoun which is often translated as "quién". "With whom" is a form of "with whom", a phrase which is often translated as "con quien". Learn more about the difference between "who" and "with whom" below.
who(
hu
)A pronoun is a word that stands in for a noun (e.g., she).
a. quién
Hello? Who is calling?¿Hola? ¿Quién llama?
I don't know who he is, but he looks a lot like my brother.No sé quién es, pero se parece mucho a mi hermano.
2. (relative)
with whom(
wihth
hum
)A phrase is a group of words commonly used together (e.g., once upon a time).
1. (general)
a. con quien (singular)
This is the doctor with whom we will be speaking tomorrow.Éste es el doctor con quien hablaremos mañana.
b. con quienes (plural)
I met Michael's brothers today, with whom he has a lot in common.Conocí a los hermanos de Michael hoy, con quienes él tiene mucho en común.
c. con quién (in questions)
Yes, my name is Peter Johnson. With whom am I speaking?Sí, me llamo Peter Johnson. ¿Con quién estoy hablando?
