People also often confuse conscious with conscience. The latter is a noun referring to one’s internal moral compass: if you hurt someone, you may find that it weighs on your conscience. The former is an adjective referring to a state of awareness of something (or everything): I am conscious.
Mucus: a noun referring to a slick/gooey material secreted by various parts of an organism.
Mucous: a noun specifying some kind of connection to mucus. Mucous membranes secrete mucus.
A brake (noun) is a thing that slows or stops a vehicle. To brake (verb) is to slow or stop. You can brake using a brake, but you don’t have to use a brake to brake; you can brake with pretty much anything. Dinghy coasting toward the dock? You can brake with your hand.
A break (noun) is something you need after a few hours on the job. To break (verb) something is to cause it to fracture (break your arm), fail (break your TV), or interrupt (circuit breaker).
If you break your brake, you may not be able to brake when you need to. If an elevator’s cables break, it can still break its fall using a built-in brake.