seasickness vs mal de mer

seasickness and mal de mer both are nouns.

Word	Noun	Adjective	Verb	Adverb
seasickness	Yes	No	No	No
mal de mer	Yes	No	No	No

As nouns, seasickness and mal de mer are synonyms defined as:

seasickness and mal de mer: motion sickness experienced while traveling on water

Other synonyms of seasickness include naupathia.

seasickness (noun)	mal de mer (noun)
motion sickness experienced while traveling on water	motion sickness experienced while traveling on water