Consider:
Where = here
When = now
What = this
How = thus
Why = (this is why)??
With the above, you could answer a question with the word on the left with just the single word on the right as an answer without additional information when the context is implicit, or can be provided with non-verbal cues such as pointing or demonstrating.
Is there a single word answer to the question "why?" to describe this reason or this is why when the context is implicit? Both therefore and because are inadequate as they require additional information.
Best Answer
A seldom used alternative to because and therefore, is wherefore.
If you want good examples, read the works of Shakespeare.