[Latin valent-, being strong, present participle of valere, to be worth.]
This ending is common in chemistry to indicate the combining power or valency of an element or radical. Though it is possible to use either Latin or Greek number prefixes, the Greek ones are much more common: monovalent (a combining power of one), divalent (of two), and so on (see the entry Number words); one with a valency of three or more is polyvalent (Greek polloi, many). The ending also appears in terms indicating the nature of the combination, as in covalent, bonding by sharing electrons, as opposed to ionic or electrovalent bonding where the attraction is electrostatic.
Outside chemistry, the same ending occurs in ambivalent (Latin ambi-, on both sides), equivalent (Latin aequi-, equally), and prevalent (Latin praevalere, have greater power, from prae, before).