marshland vs marsh

marshland and marsh both are nouns.

Word	Noun	Adjective	Verb	Adverb
marshland	Yes	No	No	No
marsh	Yes	No	No	No

As nouns, marshland and marsh are synonyms defined as:

marshland and marsh: low-lying wet land with grassy vegetation; usually is a transition zone between land and water

Other synonyms of marshland include fen, fenland.

marshland (noun)	marsh (noun)
low-lying wet land with grassy vegetation; usually is a transition zone between land and water	low-lying wet land with grassy vegetation; usually is a transition zone between land and water