The Kostel dialect ( , , ; ), in Croatian literature also eastern microdialects of Western Goran subdialect (, , , ), is a dialect spoken along the Kupa Valley in Slovenia and Croatia, around Banja Loka and Brod na Kupi. The dialect originates from Alpine Slavic, a predecessor of modern Slovene, but speakers living in Croatia self-identify as speaking Croatian. The dialect borders the Mixed KoÃÂevje subdialects to the north, the Southern White Carniolan and Eastern Goran dialect to the east, the ÃÂabranka dialect to the west, and the Goran dialects to the south and east, as well Shtokavian, which is spoken in Moravice and neighboring villages. The dialect belongs to the Lower Carniolan dialect group, and it evolved from the Lower Carniolan dialect base. Until recently, the neighboring ÃÂabranka dialect was considered part of the Kostel dialect, but it was later discovered that both dialects had evolved separately but are in process of becoming more similar to each other.
The Kostel dialect is spoken in Croatia, but the northernmost part extends into southern Slovenia. It extends from Kuà ¾elj and Gornji Turni in the west, south to Ravna Gora, as far east as Razdrto, and north to Banja Loka and Kostel. It is the southernmost Slovene dialect. Notable settlements include Kuà ¾elj, GuÃÂe Selo, Brod na Kupi, Krivac, Gornji Turni, Kupjak, Ravna Gora, Skrad, Brod Moravice, Lokvica, and à  imatovo in Croatia, and Vas, Fara, Kuà ¾elj, and Potok in Slovenia.
The border between the Kostel dialect, South White Carniolan dialect, and Mixed KoÃÂevje subdialects is somewhat unclear, and the Kostel dialect may also extend down the Kupa River on the Slovene side.
The Kostel dialect lost the difference between high- and low-pitched accent on both long and short vowels, which are still differentiated. It also underwent three accent shifts: the â , â , / â / , â , and â accent shift.
Almost all vowels have monophthongized, which sets this dialect apart from all other Lower Carniolan dialects.
Akanye is not particularly common, but ukanye is, turning word-final into or . Unstressed is reduced into , , , or . Unstressed evolved into . The Banja Loka and DelaÃÂ microdialects also have unstressed long vowels, which became unstressed after accent shifts.
Word-final mostly turned into . Palatal and have not depalatalized. If a word started with then appeared before it, and if a word started with then appeared before it. However, the dialect lost before at the beginning of words. Alpine Slovene evolved into non-sonorant , which devoices if at the end of a word or before a non-voiced consonant. The clusters and simplified into and , respectively. Other consonant simplifications also occurred, such as â .
Dual forms were fully replaced by plural forms. The future and preterit tenses are formed using the l-participle.
The priest and Slavic specialist Joà ¾e Gregoriàcollected almost 17,000 words spoken in the Slovene part of the Kostel dialect, from Srobotnik to Grgelj, which is currently still listed as belonging to the Mixed KoÃÂevje subdialects, and he published a dictionary of the Kostel dialect.