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"Cuarto" is an adjective which is often translated as "fourth", and "son las nueve" is a phrase which is often translated as "it's nine o'clock". Learn more about the difference between "cuarto" and "son las nueve" below.
cuarto, el cuarto()
An adjective is a word that describes a noun (e.g., the big dog).
a. fourth
Entra al edificio y toma el ascensor al cuarto piso.Enter the building and take the elevator to the fourth floor.
A masculine noun is used with masculine articles and adjectives (e.g., el hombre guapo, el sol amarillo).
son las nueve()
A phrase is a group of words commonly used together (e.g., once upon a time).
1. (general)
a. it's nine o'clock
Son las nueve de la noche y Alicia todavía no llegó.It's nine o'clock in the evening, and Alicia has not arrived yet.