What is the meaning of “que” and “cual” without an accent mark?

Question

What does "que" and "cual" mean without an accent mark? How do they compare when to each other? How do they compare to their accent-marked form?

Answer 1

Qué and cuál are interrogatory pronouns, and are thus used when asking questions (see relevant question):

¿Qué ha ocurrido? → What has happened?

¿Cuál es tu número de teléfono? → What is your phone number?

Qué can also be an exclamative adjective (if it is used before a noun):

¿Qué hora es? → What time is it?

Qué can also be an exclamative adverb (if it is used before an adjective):

¡Qué guapa es! → How pretty she is!

Qué can also be used in exclamations (not only in questions). So qué (with accent mark) can be used in direct or indirect questions and exclamations:

¿Qué has hecho? → What have you done?(direct question)

No sé qué hacer. → I don't know what to do. (indirect question)

¡Qué guapa es! → How pretty she is! (direct exclamation)

Ya sabe qué dura es la vida. → He already knows how hard life is. (indirect exclamation)

Without accents, they are relative pronouns:

Rebeca es la mujer con la que vas a viajar. → Rebeca is the woman with whom you are going to travel.
Rebeca es la mujer con la cual vas a viajar → Rebeca is the woman with whom you are going to travel.

Que (without the accent) can also be a conjunction:

Quiero que vengas. → I want that you go. / I want you to go.
Llámame antes de que llegues. → Call me before you arrive.