car sickness vs motion sickness

car sickness and motion sickness both are nouns.

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

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

car sickness: motion sickness experienced while traveling in a car
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 car sickness include kinetosis.

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