A crevice is a narrow crack in a surface — especially in rock, stone, or a wall. Picture a split you could slide a coin into, or that a lizard could vanish into: thin, often quite deep, not a wide gap you could walk through. Climbers and hikers use it all the time (a crevice in a cliff, a crevice in dry earth). People stretch it a little for ordinary things too — a crevice between floorboards, a crevice in an old wall — but the picture is still “a tight split”, not a hole or a cave. It is a precise, rather physical word; “crack” is the everyday cousin, but a crevice feels narrower and more like a place something could hide. You will meet it in nature writing, buildings, and science more than in chat. Though actually, English also has crevasse, which looks almost the same and comes from the same place: that one is the huge split in ice, not this small rock-crack.