Etimology
From Middle English bi cause, from bi (“by”) + cause, modelled on Old French par cause.
adverb
because (not comparable)
For the reason (that).
On account (of), for sake (of).
(by ellipsis) Used alone to refuse to provide a full answer a question begun with "why", usually taken as an anapodoton of the elided full phrase "Because I said so".
Examples
And God blessed the seuenth day, and sanctified it: because that in it he had rested from all his worke, which God created and made.
My life is ruined because of you!
conjunction
because
By or for the cause that; on this account that; for the reason that.
As is known, inferred, or determined from the fact that.
(obsolete) So that, in order that. [15th–17th c.]
Examples
I hid myself because I was afraid.
I was about to say that I had known the Celebrity from the time he wore kilts. But I see I will have to amend that, because he was not a celebrity then, nor, indeed, did he achieve fame until some time after I left New York for the West.
In plants, the ability to recognize self from nonself plays an important role in fertilization, because self-fertilization will result in less diverse offspring than fertilization with pollen from another individual.
“Perhaps it is because I have been excommunicated. It's absurd, but I feel like the Jackdaw of Rheims.” ¶ She winced and bowed her head. Each time that he spoke flippantly of the Church he caused her pain.
It must be broken, because I pressed the button and nothing happened.
I don't think he is a nice person, because he yells at people for no reason.
Simon […] set the house on fire where he was born, because nobody should point at it.
Related words
synonyms
(for the reason that): therefore, since, for, for that, forthy, for sake, forwhy (obsolete), as, inasmuch as, sith (obsolete), ∵ (mathematics symbol); see also Thesaurus:because
preposition
because
(colloquial, Internet slang) On account of, because of. [from 20th c. or before]
Examples
He rejected me because revenge, I guess.
It doesn't work because reasons.
You probably know it better, however, as explanation by way of Internet—explanation that maximizes efficiency and irony in equal measure. I'm late because YouTube. You're reading this because procrastination. As the language writer Stan Carey delightfully sums it up: “‘Because’ has become a preposition, because grammar.”