fen vs fenland

fen and fenland both are nouns.

Word	Noun	Adjective	Verb	Adverb
fen	Yes	No	No	No
fenland	Yes	No	No	No

As nouns, fen and fenland are synonyms defined as:

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

Other synonyms of fen include marsh, marshland.

fen (noun)	fenland (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
100 fen equal 1 yuan in China