When things being compared have equal characteristics, the comparison of equality is used.

The book is as good as the movie.
The boy is as tall as the girl.

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To form the comparisons of equality using adjectives or adverbs, use the following formula:

tan + adjective (adverb) + como

El libro es tan bueno como la película.
(The book is as good as the movie.)

El chico es tan alto como la chica.
(The boy is as tall as the girl.)

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To form comparisons of equality with nouns, use the following formula:

tanto(-a,-os,-as) + noun + como

Juan tiene tanto dinero como María.
(as much money as)

Él tiene tanta paciencia como ella.
(as much patience as)

Tiene tantos libros como ella.
(as many books as)

Tiene tantas plumas como ella.
(as many pens as)

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Choose the form of tanto to agree with the noun it modifies.

tanto dinero
tanta paciencia
tantos libros
tantas plumas

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When actions (not things) are being compared, and there is no adjective, use the following formula:

verb + tanto + como

Sus estudiantes aprenden tanto como mis estudiantes.
(learn as much as)

Rosario cocina tanto como Josefina.
(cooks as much as)

Las naranjas cuestan tanto como las manzanas.
(cost as much as)

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When actions (not things) are being compared, and there is an adjective, use the following formula:

verb + tan + adjective (masculine form) + como

Aquí se trabaja tan duro como ahí.
(work as hard as)

El niño juega tan poco como la niña.
(plays as little as)

Ellos duermen tan poco como ella.
(sleep as little as)