the bottom surface of any lake or other body of water
"The divers descended to the sandy floor of the shallow lake where sunken logs rested beneath them."
the lower inside surface of any hollow structure
"the floor of the pelvis"
"the floor of the cave"
the legislative hall where members debate and vote and conduct other business
"there was a motion from the floor"
The interior bottom or surface of a house or building; the supporting surface of a room.
"After dropping his keys, he quickly scanned the hardwood floor to see if they were visible beneath the scattered magazines."
In plain English: The floor is the solid surface at the bottom of a room that you walk on.
"Please be careful not to trip on the rug in the middle of the floor."
Usage: Use "floor" to refer to the solid surface at the bottom of a room that you walk on, such as carpet, wood, or tile. Do not confuse it with "ground," which refers to the earth outside a building.
surprise greatly; knock someone's socks off
"I was floored when I heard that I was promoted"
To cover or furnish with a floor.
"The renovation crew spent all day laying new tiles to finally put in a proper hardwood floor."
In plain English: To floor someone means to completely shock or overwhelm them with surprise.
"The dog floor itself when he sees the treat being poured onto his plate."
Usage: Do not use "floor" to mean covering a surface; instead, use it only when describing the action of causing someone to lose their balance or fall suddenly. You might say an unexpected joke floored him, meaning he was stunned and lost his composure, but you would never say you floored a table with carpet.
The word "floor" comes from Old English flōr, which originally meant the ground or pavement. It traveled into modern English through Middle English with this same core meaning of a flat surface.