seasickness vs motion sickness

seasickness and motion sickness both are nouns.

Word	Noun	Adjective	Verb	Adverb
seasickness	Yes	No	No	No
motion sickness	Yes	No	No	No

As nouns, motion sickness is a hypernym of seasickness; that is, motion sickness is a word with a broader meaning than seasickness:

seasickness: motion sickness experienced while traveling on water
motion sickness: the state of being dizzy or nauseated because of the motions that occur while traveling in or on a moving vehicle

Other hypernyms of seasickness include kinetosis.

seasickness (noun)	motion sickness (noun)
motion sickness experienced while traveling on water	the state of being dizzy or nauseated because of the motions that occur while traveling in or on a moving vehicle