This paper analyses the structure of copular sentences and problematizes their division into predicational, specificational, equative and identificational sentences. Our emphasis is on predicate copular sentences in which the post-copular NP can appear in the nominative or the instrumental case in Croatian, just like in some other Slavic languages. Occurrences of the instrumental case in copular predicates are extremely rare in south Slavic languages and there is some question as to when they appear at all. This paper presents the different theories about the occurrence of the instrumental case in predicative nominals (Mrázek 1964, Bailyn and Rubin 1991). Bailyn and Rubin (1991) consider the use of the instrumental case in secondary predicate adjuncts in the Russian language to be a language innovation, while Croatian and many other Slavic languages have a pattern that is found in the Old Church Slavonic and Old Russian languages. The paper also analyses Croatian grammars, written before the 20th century, with the goal of determining when the instrumental case first appeared with the copula. Many linguists (e.g. Jakobson 1936, Mrázek 1964, Wierzbicka 1980, Janda and Clancy 2002, Timberlake 2004, Geist 2006, Pereltsvaig 2007) consider that the copular sentences with the nominative or the instrumental case have different meanings in the Russian language: the nominative denotes a permanent, inalienable property of the subject, while the instrumental denotes a temporary property. This assumption is analysed in the Croatian language based on the examples from the relevant Croatian language corpora. We confirm the constraint, described in Croatian grammars, that the instrumental cannot appear with the copula in the present tense, but is possible in the perfect and future tenses. Cognitive grammar explains this by the application of the proximity principle: conceptual distance is related to formal distance. Therefore, the instrumental can appear with the copula in the perfect and future tenses, because there is distance between the subject and what he/she/it has been, or is going to become. Conversely, in the present tense there is no distance, and therefore the precopular and post-copular NPs have the same case. It is noted that nouns belonging to specific semantic groups appear in the instrumental case (profession, function, part of something, reason for something, goal, base etc.). We conclude that the instrumental case denotes temporary, acquired properties, while the nominative case denotes permanent, inalienable properties. This conclusion is drawn using examples from the relevant Croatian language corpora and based on the fact that the instrumental cannot appear with present tense and that adjectives are rarely marked with instrumental. Furthermore, these conclusions were tested by examining native speakers’ linguistic intuition. Native speakers did not recognize the semantic difference between sentences with a nominative predicate NP and an AP and instrumental. Therefore, our conclusion is that the instrumental case is related to style.

copula be; copular sentence; instrumental; nominative; Croatian language; Russian language