heme vs haem

heme and haem both are nouns.

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

As nouns, heme and haem are synonyms defined as:

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

Other synonyms of heme include haemitin, hematin, protoheme.

heme (noun)	haem (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