In the electric appliance manufacturing industry, there are three appliance classes.
In various contexts where people (or individuals of any kind) are at any time in different stages of the same general process, and all of those in the same stage are considered to constitute a class, see:
In education, a class is also a short period of teaching in a particular subject. See lesson.
In sea warfare, where individual vessels of a class of naval watercraft share essentially the same design, see navy or, under an article for a specific country, the topic of its navy.