as
adverb
Definitions
To such an extent or degree; to the same extent or degree.
Example: It's not as well made, but it's twice as expensive.
Considered to be, in relation to something else; in the relation (specified).
Example: 1865, The Act of Suicide as Distinct from the Crime of Self-Murder: A Sermon
For example; for instance. (Compare such as.)
preposition
Definitions
Introducing a basis of comparison, with an object in the objective case.
Example: They're big as houses.
In the role of.
Example: He was never seen as the boss, but rather as a friend.
conjunction
Definitions
In the (same) way or manner that; to the (same) degree that.
Example: As you wish, my lord!
At the time that; during the time when:
Being that, considering that, because, since.
Example: As it’s too late, I quit.
Introducing a comparison with a hypothetical state (+ subjunctive, or with the verb elided): as though, as if.