melena vs ordure

melena and ordure both are nouns.

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

As nouns, ordure is a hypernym of melena; that is, ordure is a word with a broader meaning than melena:

melena: abnormally dark tarry feces containing blood (usually from gastrointestinal bleeding)
ordure: solid excretory product evacuated from the bowels

Other hypernyms of melena include BM, dejection, faecal matter, faeces, fecal matter, feces, stool.

melena (noun)	ordure (noun)
abnormally dark tarry feces containing blood (usually from gastrointestinal bleeding)	solid excretory product evacuated from the bowels