More nomenclature tidbits: It’s “Principal” Components (adjective), not “Principle” Components (noun)
As a noun, principal refers to (1) one who holds a presiding position or rank, and (2) capital or property before interest, and it’s also an adjective meaning (3) first or most important in rank
Principle is only a noun. In its primary sense, it refers to a basic truth, law, assumption, or rule.
This third definition (3) is the context in which we will be using this term.