femme fatale vs siren

femme fatale and siren both are nouns.

Word	Noun	Adjective	Verb	Adverb
femme fatale	Yes	No	No	No
siren	Yes	No	No	No

As nouns, femme fatale and siren are synonyms defined as:

femme fatale and siren: a woman who is considered to be dangerously seductive

Other synonyms of femme fatale include Delilah, enchantress, temptress.

femme fatale (noun)	siren (noun)
a woman who is considered to be dangerously seductive	eellike aquatic North American salamander with small forelimbs and no hind limbs; have permanent external gills
	an acoustic device producing a loud often wailing sound as a signal or warning
	a warning signal that is a loud wailing sound
	a woman who is considered to be dangerously seductive