The word "as" can be translated to Spanish in many ways - probably dozens, and you often can't substitute one of them for another.
The trick to translating "as" to Spanish often amounts to figuring out how it functions in a sentence and coming up with a different way of expressing the same idea. While the following isn't a complete list of the ways "as" can be used and translated, it includes the most common:
In comparisons of equality: One of the most common uses of "as" in English is in pairs to indicate that two things or actions are equal. Such comparisons of equality typically are made using the phrase "tan… como" (where the ellipses represent an adjective or adverb) or "tanto… como" (where the ellipses represent a noun and tanto changes in form to match the noun in number and gender).
- Never in my life have I been as happy as I am today. Nunca en mi vida había sido tan feliz como hoy.
- I also fell in love with my first teacher, as crazily as is possible for a child. Yo también me enamoré de mi primera maestra, tan locamente como es posible en un niño.
- You could earn as much money as you want. Podrías ganar tanto dinero como usted quieras.
To mean "in the way that": In informal English, "as" with this meaning can often be substituted with "like" or, less frequently, "how." Como often works as a translation.
- I would llike to know if you think as I think. Me gustaria saber si piensas como pienso.
- Leave it as it is. Déjalo como está.
- As you all know, the first item on the agenda is the election of the president. Como saben todos ustedes, el primer punto del orden del día es la elección del presidente.
- As I was saying, everything was perfect. Como iba diciendo, todo era perfecto.
- He eats as if it were going to be his last time. Come como si fuera a ser su última vez.
To mean "because":" When used to express causation, "as" can be translated as explained in our lesson on causation:
- He was looking for water as he was thirsty. Buscaba agua porque tenía sed.
- As I didn't have any money, I couldn't buy the car. Como yo no tenía dinero, no pude comprar el coche.
To mean "while" or "when": Mientras (and sometimes cuando) can usually be used to indicate simultaneous actions:
- As he was studying he watched CNN. Mientras estudiaba veía la CNN.
- As we were eating, I decided to tell it to all of us who were there. Mientras comíamos, decidí decírselo a todos los que estábamos allí.
To refer to a role or position: When "as" introduces an adverbial phrase, it can often be translated using como:
- He walks as a thief in the night. Anda como ladrón en la noche.
- It is a portrait of Jonah as as a young artist. Es retrato de Jonah como joven artista.