Why is a pseudo-class so called?

Question

a:hover

Why is it called a "pseudo-class"?

Are there any similarities with the concept of "class"?

Answer 1

In CSS terms, a class is a selector that starts with a full stop, e.g.

.foo { ... }

It would be used in the form

<div class="foo">

This use of "class" is more in the sense "a set or category of things having a common characteristic and differentiated from others by kind or quality", rather than borrowing from OO terminology.

A pseudo class is "not quite a real one" as the user agent defines when and/or how much content qualifies (like :hover, :active, etc).