motion sickness vs ailment

motion sickness and ailment both are nouns.

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

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

motion sickness: the state of being dizzy or nauseated because of the motions that occur while traveling in or on a moving vehicle
ailment: an often persistent bodily disorder or disease; a cause for complaining

Other hypernyms of motion sickness include complaint, ill, nausea, sickness.

motion sickness (noun)	ailment (noun)
the state of being dizzy or nauseated because of the motions that occur while traveling in or on a moving vehicle	an often persistent bodily disorder or disease; a cause for complaining