infinitely

As an adjective infinitesimal

is incalculably, exceedingly, or immeasurably minute; vanishingly small.

As a noun infinitesimal

is a non-zero quantity whose magnitude is smaller than any positive number (by definition it is not a real number).

As an adverb infinitely is

in an infinite manner; as of anything growing without bounds; endlessly.

Indefinetly is likely misspelled.

Indefinetly has no English definition.

As an adverb infinitely is

in an infinite manner; as of anything growing without bounds; endlessly.

As adverbs the difference between infinitely and unendly

is that infinitely is in an infinite manner; as of anything growing without bounds; endlessly while unendly is in an unendly or infinite manner; infinitely; unendingly.

As an adjective unendly is

having no end; infinite; endless; unending.

As adverbs the difference between infinitely and numberlessly

is that infinitely is in an infinite manner; as of anything growing without bounds; endlessly while numberlessly is in a numberless way; uncountably, infinitely.