family Echeneidae vs family Echeneididae

family Echeneidae and family Echeneididae both are nouns.

Word	Noun	Adjective	Verb	Adverb
family Echeneidae	Yes	No	No	No
family Echeneididae	Yes	No	No	No

As nouns, family Echeneidae and family Echeneididae are synonyms defined as:

family Echeneidae and family Echeneididae: fishes having a sucking disk on the head for clinging to other fishes and to ships

Other synonyms of family Echeneidae include Echeneididae.

family Echeneidae (noun)	family Echeneididae (noun)
fishes having a sucking disk on the head for clinging to other fishes and to ships	fishes having a sucking disk on the head for clinging to other fishes and to ships