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"Una" is a form of "una", a noun which is often translated as "one". "Cuarenta" is an adjective which is often translated as "forty". Learn more about the difference between "cuarenta" and "una" below.
cuarenta()
A masculine noun is used with masculine articles and adjectives (e.g., el hombre guapo, el sol amarillo).
la una()
A feminine noun is almost always used with feminine articles and adjectives (e.g., la mujer bonita, la luna llena).
1. (time)
