is a specific kind of: plant order.

has as a member: family Naiadaceae, family Najadaceae, naiad family, Naiadaceae, Najadaceae | Alismataceae, family Alismataceae, water-plantain family | family Hydrocharidaceae, family Hydrocharitaceae, frog's-bit family, frogbit family, Hydrocharidaceae, Hydrocharitaceae | family Potamogetonaceae, pondweed family, Potamogetonaceae | arrow-grass family, family Juncaginaceae, family Scheuchzeriaceae, Juncaginaceae, Scheuchzeriaceae | family Zannichelliaceae, Zannichelliaceae | eelgrass family, family Zosteraceae, Zosteraceae.

is a member of: class Liliopsida, class Monocotyledonae, class Monocotyledones, Liliopsida, Monocotyledonae, Monocotyledones.