siren vs femme fatale

siren and femme fatale both are nouns.

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

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

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

Other synonyms of siren include Delilah, enchantress, temptress.

siren (noun)	femme fatale (noun)
eellike aquatic North American salamander with small forelimbs and no hind limbs; have permanent external gills	a woman who is considered to be dangerously seductive
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