inside
UK: ɪnˈsaɪd | US: ɪnˈsaɪd
n. the inner side or surface of something
adv. within or into a building, room, etc.
adj. situated on or in the inner part
prep. within the interior of
The word "inside" combines the Old English preposition "in" (meaning "within") and "side" (from Old English "sīde," meaning "flank" or "edge"). It emerged in Middle English (14th century) to describe spatial relationships, emphasizing containment or interiority. The logic is straightforward: "in" locates something, while "side" specifies the boundary or surface being referenced. Over time, it expanded from literal physical spaces to abstract contexts (e.g., "inside information").
She left her keys inside the car.
The door was locked from the inside.
He knows the inside details of the project.
Turn the shirt inside out before washing.
The noise came from inside the house.