melena vs melaena

melena and melaena both are nouns.

Word	Noun	Adjective	Verb	Adverb
melena	Yes	No	No	No
melaena	Yes	No	No	No

As nouns, melena and melaena are synonyms defined as:

melena and melaena: abnormally dark tarry feces containing blood (usually from gastrointestinal bleeding)

melena (noun)	melaena (noun)
abnormally dark tarry feces containing blood (usually from gastrointestinal bleeding)	abnormally dark tarry feces containing blood (usually from gastrointestinal bleeding)