Equative is a case prototypically expressing the standard of comparison of equal values ("as… as a …"). The equative case has been used in very few languages in history. It was used in the Sumerian language, where it also took on the semantic functions of the essive case ("in the capacity of…") and similative case ("like a…").
For Sumerian, the equative was formed by adding the suffix -gin7 to the end of a noun phrase. In its similative function:
lugal, "king"; lugal-gin7, "kinglike", "like a king": nitah-kalaga; "mighty man"; nitah-kalaga-gin7, "like a mighty man"For Ossetic it is formed by the ending -ау [aw]:
фæт, "arrow"; фæтау, "arrowlike" Ницы фенæгау йæхи акодта, lit. "nothingseer-like himself made" ("[he or she] pretended to see nothing").It is also found in the Turkic Khalaj language and in languages from South America like Quechua, Aymara, Uro and Cholón.
Welsh, though it has no equative case of nouns, has an equative degree of adjectives, shown normally by the suffix -ed: for example, "hyned" (â), meaning "as old" (as).
Sireniki Eskimo had an equative (or comparative) case for describing similarities between nouns.
Finnish has the derivational suffixes -mainen and -lainen that have the same meaning, but form new words rather than functioning as grammatical case suffixes. For example, kuningas ~ kuningasmainen "king ~ kinglike".