undulation vs sinusoid

undulation and sinusoid both are nouns.

Word	Noun	Adjective	Verb	Adverb
undulation	Yes	No	No	No
sinusoid	Yes	No	No	No

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

Other hyponyms of undulation include sine curve.

undulation (noun)	sinusoid (noun)
(physics) a movement up and down or back and forth	tiny endothelium-lined passages for blood in the tissue of an organ
wavelike motion; a gentle rising and falling in the manner of waves	the curve of y=sin x
an undulating curve