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"Atrás" is an adverb which is often translated as "behind", and "desde hace" is a phrase which is often translated as "for". Learn more about the difference between "atrás" and "desde hace" below.
atrás()
An adverb is a word that describes a verb, an adjective, or other adverbs (e.g., to run quickly, very tired).
1. (position)
2. (movement)
desde hace()
A phrase is a group of words commonly used together (e.g., once upon a time).