Also found in: Dictionary, Thesaurus, Medical, Acronyms, Wikipedia.
a genus of plants of the family Najadaceae. The plants are annual aquatic herbs. The almost opposite or pseudoverticil-late leaves are for the most part linear; they have serrate or sinuate-dentate margins and a short spathe. The stems are generally stiff, brittle, and strongly branched. There are about 35 species of Najas, distributed almost everywhere in lakes, oxbows, and estuaries, as well as along seashores. Six species are found in the USSR, in the European part, the Caucasus, Siberia, the Far East, and Middle Asia. Fossils of many species of Najas have been found.