Sindarin

Sindarin was the language of the Sindar, those Teleri which had been left behind on the Great Journey of the Elves. It was derived from an earlier language called Common Telerin. When the Noldor came back to Middle-earth, they adopted the Sindarin language, although they believed their native Quenya more beautiful.
Sindarin became the language of the Noldor because of the command of King Elu Thingol of Doriath. Upon learning of the Kinslaying at Alqualondë, he declared that Quenya, the language of the Noldor, should be prohibited in his lands. As the Noldor were dwelling in a Sindarin-speaking land, and because of the decree of Thingol though it did not directly affect them, they gradually switched entirely to Sindarin. Their names were also changed to Sindarin, such as Finwë-Ñolofinwë to Fingolfin, and Turukáno to Turgon.
When the Elves of Beleriand first encountered the dwarves, they could not understand a word of the tongue of the Dwarves. Dwarves were swift to learn and indeed were more willing to learn Sindarin than to teach their own to those of alien race.
The written script alphabet of the Elven languages is typically Tengwar, although Cirth (itself originally intended specifically for Sindarin) can also be used.