Cassette, sprocket, gear, chainring, chainwheel, pulley, are all interchangeable.

High gear and low gear and big and small gear can all be interchanged. (high/big can mean larger, or a higher derailleur position, or closer to the frame, or harder to push or faster pedaling.

Wheel can mean anything from wheel, to hub, tube, tire, or rim.

Cranks can be levers.

Number of "speeds" can be counted, added, and multiplied together in almost any combination you like, but higher is always better.

Road bikes are skinny bikes, or thin wheeled bikes.