Because "sprocket" is the name decided on for a toothed wheel that hooks up to a chain, and that's how most bicycles are powered.
Due to the fact that there's more than one on a bike, people have also had to come up with other names to be able to tell them apart.
Adult bikes have chainwheel(s) up by the pedals and sprockets (or maybe a cassette, made up of several sprockets) by the rear wheel.
A BMX, confusing enough, can have the sprocket by the pedals, and a driver by the rear wheel.
It depends on whether you are talking about the front sprocket (the one at the pedals, called a chainring) or the sprocket at the rear derailleur. The lowest gear at the front is the smallest sprocket/chainring. The lowest gear at the rear is the largest sprocket. So if you combine the smallest sprocket at the front with the largest sprocket in the rear you have the lowest gear available on your bike.
Chain is on the smallest sprocket on the crank and on the largest sprocket on the rear wheel
The function of a cassette sprocket in a bicycle's gear system is to provide different gear ratios, allowing the rider to adjust the resistance and speed when pedaling.
The rear bike sprocket is a gear that helps transfer power from the pedals to the rear wheel. It allows the rider to adjust the resistance and speed of the bike by changing gears. The size of the sprocket affects the bike's speed and ability to climb hills. Overall, the rear sprocket plays a crucial role in the performance and efficiency of a bicycle.
25/9 gear ratio
Even slower
In the drive train you have the front chainwheel/ring and the rear sprocket that both engage the chain. The pointy bits on sprocket and chainwheel which allows the chain to grip are called teeth. The ratio between the tooth counts is what determines which gear ratio the bike has.
On a bike there's one(or more) front sprocket(s) by the pedals connected by a chain to one(or more) rear sprocket(s) by the rear wheel. As the wheel isn't driven directly by the pedals, and there's usually a difference in size between the front & rear sprocket this constitutes a gear.
The derailleur clutch is a component in the bike's gear system that can be either on or off, depending on the specific model and design of the bike.
The smallest sprocket is usually referred to as the "cog" and is commonly found on the rear wheel of a bicycle. It is designed to mesh with the chain and is typically the one with the fewest number of teeth among all the sprockets on the bike.
First gear on a bicycle with external/derailer gears is with the chain on the smallest chainwheel(by the pedals) and the biggest sprocket(by the rear wheel).
If its a road bike, chances are its geared exactly correctly to match power with top speed. Essentially if you add teeth to the rear wheel sprocket, you will shorten the gearing and the engine will hit top revs in top gear before the bike reaches top speed. If you add teeth to the engine sprocket, the opposite effect, less torque in top gear leaving the bike short on top speed.