Origin: Germanic Old English prefix
Within has 4 different meanings across 2 categories:
In the context of which the present document or ruling is made.
"The new regulations will take effect within, so they apply immediately to any current contracts under review."
In plain English: Within means being inside something rather than outside of it.
"The within limits of my budget are strictly enforced for this trip."
In or into the interior; inside.
"The cat curled up within the warm box to sleep."
In plain English: Within means happening inside something or during a specific amount of time without going outside those limits.
"The train will arrive within five minutes."
In the inner part, spatially; physically inside.
"The cat hid within the dark corners of the closet."
The word comes from the combination of the words with and in. It has been used in English since before the 12th century to mean being inside or enclosed by something.