qual

The root qual comes from Latin quālis, an old question word meaning "of what kind? of what sort?" When a Roman asked quālis est?, they weren't asking how much (that was quantus) — they wanted to know the nature of a thing, its character, what sort it was. This single question, "what kind?", is the seed of the whole family.

The Roman writer Cicero needed a word to translate a Greek philosophical idea, so he coined the abstract noun quālitās — literally "of-what-kind-ness" — the property of being a certain sort. That word came into English as quality. At first it simply meant "a characteristic, a trait" (a person's good and bad qualities). Only later did it pick up the meaning of degree of excellence — high quality, low quality — because asking "what kind is it?" naturally slides into "how good is it?"

The verb branch grew from quālis + -ficāre ("to make") → qualify, literally "to make of a certain kind." If you qualify for a job, you have been made into the right kind of person for it — you meet the standard. From this come qualified (made into the right kind = competent, certified) and qualification (the thing that makes you the right kind = a credential, a degree).

But qualify has a second, sneakier sense. To say "what kind" is also to set limits: if I qualify my praise, I specify which kind of praise it is — praise with conditions attached. So qualify also means "to limit, to modify, to add a condition." This double life produces English's nicest little irony: qualified can mean "competent" (a qualified doctor) or "limited, hedged" (qualified support — support with strings attached). And its opposite unqualified mirrors the trick: it means both "not competent" (an unqualified applicant) and "with no limits, absolute" (an unqualified success). Same word, opposite directions — one about people, one about conditions.

Notice that qual (kind, quality) sits directly opposite quant (how much, quantity). The two were a matched pair in Latin and still are in English: quality vs quantity, qualitative vs quantitative. Whenever you see qual, think character and kind, never amount.