vodným

Vodním is the instrumental singular form of the Czech adjective vodní, meaning water-related or pertaining to water. The base form vodní is used to describe nouns that relate to water, such as vodní plocha (water surface) or vodní tok (watercourse). The adjective is derived from voda (water) with the adjectival suffix -ní, a common formation in Czech.

In terms of grammar, vodní declines as other adjectives. The instrumental singular masculine and neuter form is vodním, used after prepositions or with verbs in instrumental constructions, for example s vodním režimem (with a water regime) or vodním útvarem (by a body of water). The feminine instrumental forms differ, and agreement with the noun is required.

Common contexts for vodní include hydrology, geography, environmental science, engineering, and everyday language. Frequently encountered noun phrases include vodní tok (watercourse), vodní plocha (water surface), vodní nádrž (water reservoir), vodní elektrárna (hydroelectric power plant), and vodní zdroj (water source). The form vodním is not a standalone noun but a grammatical form used to modify a noun.

Etymologically, vodní comes from voda, the Slavic root for water, with the suffix -ní. It shares cognates across Slavic languages, reflecting a common semantic field of water-related phenomena.

This article notes that while vodní is a common adjective, its exact form, including vodním, must agree with the noun in gender, number, and case within Czech grammar.