As a non-native English speaker, one of the most recurring confusions I've had, and which I can't seem to ever get straight, is how to refer to those mechanical "thingies" you often see in old machines and in cartoon depictions of machines.
Are they "cogs", "wheels", "cogwheels", "cog wheels", "sprockets", or something different entirely? I suspect that there are multiple synonyms in English and also that there are different variations of the same basic idea, given different words, which is probably what confuses me.
The one I imagine is like a metallic "circle" (although usually not very flat) with "teeth" around it, made to hook into another such object for the purpose of doing some kind of mechanical work in an efficient and predictable manner. Sometimes, they seem to not have teeth but instead a belt. I don't know if these are considered distinct objects or all the same.
I assume that there are still large, industrial machines that use these, but I primarily associate them with the 1800s and first half of the 1900s. They also exist as very flat and small versions in mechanical watches.