Wordnet 3.0
NOUN (1)
1. 
 ferns: a large family that in some classification systems has been subdivided into several families (including Aspleniaceae and Blechnaceae and Davalliaceae and Dennstaedtiaceae and Dryopteridaceae and Oleandraceae and Pteridaceae); 
[syn: Polypodiaceae, family Polypodiaceae]
WordNet (r) 3.0 (2006):
Polypodiaceae
    n 1: ferns: a large family that in some classification systems
         has been subdivided into several families (including
         Aspleniaceae and Blechnaceae and Davalliaceae and
         Dennstaedtiaceae and Dryopteridaceae and Oleandraceae and
         Pteridaceae) [syn: Polypodiaceae, family Polypodiaceae]