Characteristics
The Kajkavian area of Croatia is bordered on the northwest by Slovene language territory. It is bordered on the east and southeast by Štokavian dialects roughly along a line that was the former division between Civil Croatia and the Habsburg Military Frontier; in southwest along Kupa and Dobra rivers, it persisted in ancient (medieval) contact with Čakavian dialects.
Near relation exists with the Prekmurian language (variant of Slovene in Prekmurje and Hungary). The speakers of Prekmurian are Slovenes and Hungarian Slovenes who belonged to the Archdiocese of Zagreb during the Habsburg era. Higher amounts of correspondences between the two exist in inflection and vocabulary.
Some Kajkavian words bear a closer resemblance to other Slavic languages (such as Russian) than they do to Štokavian or Čakavian. For instance gda seems (at first glance) to be unrelated to kada, however, when compared to the Russian когда, the relationship becomes more apparent, at the same time in Slovene: kdaj, in Prekmurian gda, kda. Kajkavian kak (how) and tak (so) are exactly like their Russian cognates, as compared to Štokavian and Čakavian kako and tako, in Prekmurian in turn tak, kak (in Slovene like Chakavian: tako, kako). (This vowel loss occurred in most other Slavic languages; Štokavian is a notable exception, whereas the same feature of Macedonian is probably not a Serbian influence, as the word is preserved in the same form in Bulgarian, to which Macedonian is much closer related than to Serbian.)
Another distinctive feature of Kajkavian is the use of another future tense. Instead of Štokavian and Čakavian future I ("ću", "ćeš", and "će" + infinitive), Kajkavian speakers use future II ("bum", "buš" and "bu" + active verbal adjective). Future II in standard Croatian can only be used in subordinate clauses to refer to a condition or an action which will occur before other future action. For example, the phrase "I'll show you" is "Ti bum pokazal" in Kajkavian whereas in standard Croatian it is "Pokazat ću ti". This is a feature shared with Slovene, and also the Prekmurian language, Slovenian: bom, boš, bo; Prekmurian: Bom, boš, bou.
Read more about this topic: Kajkavian Dialect