hop vs hop on

hop is a noun but hop on is not a noun.

Word	Noun	Adjective	Verb	Adverb
hop	Yes	No	Yes	No
hop on	No	No	Yes	No

hop (noun)	hop on (noun)
the act of hopping; jumping upward or forward (especially on one foot)
an informal dance where popular music is played
twining perennials having cordate leaves and flowers arranged in conelike spikes; the dried flowers of this plant are used in brewing to add the characteristic bitter taste to beer

hop (verb)	hop on (verb)
jump lightly	get up on the back of
make a jump forward or upward
jump across
traverse as if by a short airplane trip
move quickly from one place to another
travel by means of an aircraft, bus, etc.