Rusalka is a hypernym of siren.
As nouns the difference between siren and rusalka
is that
siren is (
original sense) One of a group of nymphs who lured mariners to their death on the rocks while
rusalka is in Slavic mythology, a female water spirit that leads handsome men to their deaths underwater.
As a verb siren
is to make a noise with, or as if with, a siren.
As an adjective siren
is relating to or like a siren.