endless

As a noun taxonomy

is the science or the technique used to make a classification.

As an adjective endless is

having no end.

As adjectives the difference between regular and endless

is that regular is while endless is having no end.

As an adverb regular

is regularly.

As adjectives the difference between endful and endless

is that endful is full of ends or aims; characteristic of having a goal, target, or specific agenda; ambitious; busy while endless is having no end.

As adjectives the difference between endless and unendly

is that endless is having no end while unendly is having no end; infinite; endless; unending.

As an adverb unendly is

in an unendly or infinite manner; infinitely; unendingly.

As adjectives the difference between endless and unexhaustible

is that endless is having no end while unexhaustible is not exhaustible; endless.