The majority of the population speaks Gilaki as their first
Language while many children, particularly in the cities, tend to use Standard Persian amongst themselves.
The Gilaki
Language is a Caspian
Language, and a member of the northwestern Iranian
Language branch, spoken in Iran's Gīlān Province.
The
Language is divided into three dialects: Western Gilaki, Eastern Gilaki, and Galeshi (in the mountains of
Gilan).
Furthermore, the Gilaki
Language is closely related to Mazanderani, and the two languages have similar vocabularies.
The western and eastern dialects are separated by the Sefid River. According to Ethnologue, there were more than 3 million native speakers of Gilaki in 1993.
Example for noun-noun possessives in Western Gilaki: məhin zakan (Mæhin's children) (Bæče-ha-ye Mæhin in Persian), Baγi gulan (garden flowers) (Gol-ha-ye Baγ in Persian).
In Eastern Gilaki: Xirsi Kuti (bear cub) (Bæč-e Xers in Persian).
Example
...see more for adjectival modification: Western Gilaki: pilla-yi zakan (big children), Surx gul (red flower). Eastern Gilaki: Sərd aw (cold water) (ɑb-e særd in Persian), kul čaqu (dull knife) (čaqu-ye kond in Persian).
Gilan has some Azerbaijani-speaking people in Astara and Manjil. The northern part of the province is inhabited by Talysh people. The Kurdish Language is used by some Kurds who have moved from Arbil to the Amarlu region.
The Language of Rudbar is Tati. Gilanis call themselves gilamard, which is a combination of 'Gil' and 'Amard.'
Reference: wikipedia.org