The definition online says that the teeth of the gears are cogs, which I'd never heard of before.

Both are from Hanna-Barbera. There is also a cartoon called The Roman Holidays, which is The Flintstones, but set in Rome.

cog
noun
ˈkäg
1 : a tooth on the rim of a wheel or gear

Can you share an image of what you describe as a single cog?

To be precise, that’s a cogwheel. There are six cogs around the cogwheel in your image. The word “cog” refers specifically to the teeth around the wheel, not the wheel itself. The cogwheel may be colloquially called a cog, but it’s technically inaccurate; If you told a watchmaker that their watch was missing a single cog, it would have a very different meaning than if you told them it was missing a single cogwheel.

That's a gear with six cogs.