⇒ In Spanish, almost any adjective can be used as a noun.

⇒ Most of the time these noun will be translated into English as the ____ one, where the blank is an adjective in English.

Quiero la roja. I want the red one.

Compré las nuevas. I bought the new ones.

Vi una casa grande y una pequeña. I saw a large house and a small one.

⇒ Adjectives are often used as nouns to refer to a noun that was recently mentioned.

¿Te gusta la falda verde o la falda negra? - Me gusta la negra. Do you like the green skirt or the black skirt? - I like the black one.

⇒ To use an adjective as a noun, you simply add an article. The article must match the noun it refers to in gender and number.

Examples:

Adjective	Singular Masculine Noun Form	Singular Feminine Noun Form	Plural Masculine Noun Form	Plural Feminine Noun Form
rojo (red)	el rojo	la roja	los rojos	las rojas
nuevo (new)	el nuevo	la nueva	los nuevos	las nuevas
barato (cheap)	el barato	la barata	los baratos	las baratas

Me gusta el vestido azul, pero el rojo es más barato. I like the blue dress, but the red one is cheaper.

⇒ Since the noun vestido is masculine and singular, rojo is also masculine and singular.

⇒ Remember that when a person is the direct object of a verb, you must use the personal a.

⇒ When a precedes el, they combine to form the contraction al

⇒ This same contraction rule applies to de + el, which together form del

¿Conoces al hombre viejo o al joven? Do you know the old man or the young one?

¿Quieres hablar del libro nuevo o del viejo? Do you want to talk about the new book or the old one?

⇒ Demonstrative adjectives may also used with this type of noun.

¿Ves esos perros? Aquel pequeño se llama Albus. See those dogs? The small one is called Albus.

⇒ You can use adjectives as nouns with the neuter article lo to refer to general or abstract senses.

⇒ It's often translated into English as the ____ thing or what's where the blank is an adjective.

Lo bueno es que estamos juntos. The good thing is that we're together.

Lo bonito de este edificio es el jardín que tiene en el techo. What's beautiful about this building is the garden on the roof.

Lo mío es el cine. Movies are my thing.