one of four subclasses or superorders of Monocotyledones; comprises about 19,000 species in 25 families of mostly terrestrial herbs especially of moist places including: Cyperaceae; Gramineae; Bromeliaceae; and Zingiberaceae

Commelinidae is a botanical name at the rank of subclass. of the subclass will vary with the being used (there are many such systems); the only requirement being that it includes the family Commelinaceae.