Wordnet 3.0
NOUN (1)
1. 
 one of four subclasses or superorder of Monocotyledones; 
 comprises about 6400 species in 5 families of trees and shrubs and terrestrial herbs and a few free-floating aquatics including: Palmae; 
 Araceae; 
 Pandanaceae and Lemnaceae; 
[syn: Arecidae, subclass Arecidae]
WordNet (r) 3.0 (2006):
subclass Arecidae
    n 1: one of four subclasses or superorder of Monocotyledones;
         comprises about 6400 species in 5 families of trees and
         shrubs and terrestrial herbs and a few free-floating
         aquatics including: Palmae; Araceae; Pandanaceae and
         Lemnaceae [syn: Arecidae, subclass Arecidae]