Gilaki (گیلٚکي زٚوؤن romanized: ɡilɵki zɵvön) is an Iranian language of the Northwestern branch, spoken in south of Caspian Sea by Gilak people. Gilaki is closely related to Mazandarani.^[2] The two languages of Gilaki and Mazandarani have similar vocabularies.^[3][4][5][6] The Gilaki and Mazandarani languages (but not other Iranian languages)^[7] share certain typological features with Caucasian languages (specifically Kartvelian language),^[7][8][9] reflecting the history, ethnic identity, and close relatedness to the Caucasus region and Caucasian peoples of the Gilak people and Mazandarani people.

The language is divided into three dialects: Western Gilaki, Eastern Gilaki^{[10][11][12][13]} and Galeshi/Deylami.^[14][15] The western and eastern dialects are separated by the Sefid River,^[16] while Galeshi is spoken in the mountains of eastern Gilan and western Mazandaran.^[15]

There are three main dialects but larger cities in Gilan have slight variations to the way they speak. These "sub-dialects" are Rashti, Rudbari, Some’e Sarai, Lahijani, Langerudi, Rudesari, Bandar Anzali, Fumani, Alamouti and Taleghani.^[5]

Gilaki, which has two main dialect types, eastern and western, with the Safidrūd River as the general border, is a member of the Caspian subgroup. ^[17] There are many subdialects of Gilaki, and, progressing to the east, it gradually blends into Mazandarani. The intermediate dialects of the area between Tonokābon and Kalārdašt serve as a transition between Gilaki and Mazandarani. The differences in forms and vocabulary lead to a low mutual intelligibility with either Gilaki or Mazandarani, and so these dialects should probably be considered a third separate language group of the Caspian area.^[18] In Mazandaran, Gilaki is spoken in the city of Ramsar and Tonekabon. Although the dialect is influenced by Mazandarani, it is still considered a Gilaki dialect.^[19][20]

Furthermore, the eastern Gilaki dialect is spoken throughout the valley of the Chalus river.^[21]

Apart from four Turkish-speaking villages higher up, the inhabitants of Alamut speak Gilaki and those of Rudbar Tati.^[22] In Qazvin province, Gilaki is spoken in northern parts of the province, in Alamut.^[23][24]

Gilaki, is an inflected and genderless language. It is considered SVO, although in sentences employing certain tenses the order may be SOV.^[25]

Gilaki is the language of the majority of people in Gilan province and also a native and well-known language in Mazandaran, Qazvin and Alborz provinces. Gilaki is spoken in different regions with different dialects and accents.^{[26][27][28][29][30][12][13][11][31]} The number of Gilaki speakers is estimated at 3 to 4 million.^[32][33][34] Ethnologue reports that the use of Gilaki is decreasing as the speaker population is decreasing.^[35]

Gilaki has the same consonants as Persian, but different vowels. Here is a table of correspondences for the Western Gilaki of Rasht, which will be the variety used in the remainder of the article:

There are nine vowel phonemes in the Gilaki language:

The consonants are:

The verb system of Gilaki is very similar to that of Persian. All infinitives end in -tən/-dən, or in -V:n, where V: is a long vowel (from contraction of an original *-Vdən). The present stem is usually related to the infinitive, and the past stem is just the infinitive without -ən or -n (in the case of vowel stems).

Gilaki employs a combination of quasi-case endings and postpositions to do the work of many particles and prepositions in English and Persian.

Gilaki adjectives come before the noun they modify, and may have the genitive "case ending" -ə/-i. They do not agree with the nouns they modify.

• Example for adjectival modification: Western Gilaki: pilla-yi zakan (big children), Surx gul (red flower). Eastern Gilaki: Sərd ow (cold water) (ɑb-e særd in Persian), kul čaqu (dull knife) (čaqu-ye kond in Persian).