The prolative case (abbreviated PROL), also called the vialis case (abbreviated VIA), prosecutive case (abbreviated PROS), traversal case, mediative case, or translative case, is a grammatical case of a noun or pronoun that has the basic meaning of "by way of" or "via".
In Finnish, the prolative case follows an established application in a number of fossilized expressions to indicate "by (medium of transaction)". It can be used in other constructions, but then it does not sound 'natural'. Examples would be "postitse" ("by post"), "puhelimitse" ("by telephone"), "meritse" ("by sea"), "netitse" ("over the Internet"). A number of Finnish grammarians classify the prolative form as an adverb because it does not require agreement with adjectives like other Finnish cases. This claim is not true, however, because an adjective will agree with the prolative: "Hän hoiti asian pitkitse kirjeitse."
The prolative exists in a similar state in the Estonian language.
Basque grammars frequently list the nortzat / nortako case (suffix -tzat or -tako) as "prolative" (prolatiboa). However, the meaning of this case is unrelated to the one just described above for other languages and alternatively has been called "essive / translative", as it means "for [something else], as (being) [something else]"; e.g., hiltzat eman "to give up for dead", lelotzat hartu zuten "they took him for a fool". The meaning "by way of" of the case labelled prolative in the above languages is expressed in Basque by means of the instrumental (suffix -[e]z).
- Haspelmath, Martin. Terminology of Case in Handbook of Case, Oxford University Press, 2006.
- Mäkinen, Panu. "Finnish Grammar - Adverbial Cases". users.jyu.fi. University of Jyväskylä. Retrieved 6 March 2015.
- Länsimäki, Maija. "Kirjeitse annettu määräys. Suomen kielen prolatiiveista". Retrieved 13 April 2015.
- Korpela, Jukka. "Finnish Cases". www.cs.tut.fi. Retrieved 13 April 2015.
- Check for example: Ilari Zubiri and Entzi Zubiri's Euskal Gramatika Osoa (Bilbao: Didaktiker, 1995); the declension reference at the website of the Basque Autonomous Government's Institute for Euskaldunization and Alphabetization of Adults (HABE); etc.
- Jon D. Patrick, Ilari Zubiri: A Student Grammar of Euskara (Munich: Lincom Europa, 2001) 
- Examples (translated from Spanish) given in Luis Baraiazarra's Diccionario 3000 Hiztegia (available online at euskadi.net), under the entry for Spanish "dar" .
- Tapani Salminen (2008-10-06). "Tundra Nenets". Department of Finno-Ugrian Studies, University of Helsinki, Finland. Retrieved 2008-12-30.
- Sechenbaatar [Sečenbaγatur], Borjigin. 2003. The Chakhar dialect of Mongol: a morphological description. Helsinki: Finno-Ugrian society. ISBN 952-5150-68-2