vesipähkinä

Noun

 * 1) water caltrop either of closely related water plants, West Eurasian or East Asian
 * 2) water caltrop edible seed of these plants

Usage notes

 * This term primarily refers to but is occasionally used of the Asian plant as well, as it has no Finnish (apparently English neither) common name of its own. To add to the terminological confusion, both T. natans and T. bicornis are also called water chestnut in English, sharing this common name with another Asian species, called  in Finnish.