Is a cultivar a subspecies, a morph, a variety , a sport, or, are all these terms roughly interchangeable?

Why, in the scientific name of a cultivar, does no indication of specific parentage appear? Because it'have to include both sides to eliminate discrimination, or, simply because it would be too cumbersome? (E.g. Clematis 'candida')

Is a cultivar a subspecies, a morph, a variety , a sport, or, are all these terms roughly interchangeable?
Morph, variety and sport could all be essentially interchangable. A subspecies is properly a geographically

delimited variant of a species population, distinguishable from the other members of the species by some trait or traits.

A cultivar is simply the cultivated form of some plant. It may be just the offspring from a single seed, propagated by

vegetative means after the seedling matures.