motion vs nod

motion and nod both are nouns.

Word	Noun	Adjective	Verb	Adverb
motion	Yes	No	Yes	No
nod	Yes	No	Yes	No

As nouns, nod is a hyponym of motion; that is, nod is a word with a more specific, narrower meaning than motion:

motion: the use of movements (especially of the hands) to communicate familiar or prearranged signals
nod: a sign of assent or salutation or command

As verbs, nod is a hyponym of motion; that is, nod is a word with a more specific, narrower meaning than motion:

motion (noun)	nod (noun)
a change of position that does not entail a change of location	the act of nodding the head
the act of changing location from one place to another	a sign of assent or salutation or command
the use of movements (especially of the hands) to communicate familiar or prearranged signals
a formal proposal for action made to a deliberative assembly for discussion and vote
a natural event that involves a change in the position or location of something
an optical illusion of motion produced by viewing a rapid succession of still pictures of a moving object
a state of change

motion (verb)	nod (verb)
show, express or direct through movement	be almost asleep
	let the head fall forward through drowsiness
	lower and raise the head, as to indicate assent or agreement or confirmation
	express or signify by nodding
	sway gently back and forth, as in a nodding motion