haem vs heme

haem and heme both are nouns.

Word	Noun	Adjective	Verb	Adverb
haem	Yes	No	No	No
heme	Yes	No	No	No

As nouns, haem and heme are synonyms defined as:

haem and heme: a complex red organic pigment containing iron and other atoms to which oxygen binds

Other synonyms of haem include haemitin, hematin, protoheme.

haem (noun)	heme (noun)
a complex red organic pigment containing iron and other atoms to which oxygen binds	a complex red organic pigment containing iron and other atoms to which oxygen binds