In 'The Lord of the Rings' the Elvish language Sindarin is based on what real language?

There is no language called "Nordic". Sindarin is more inspired by Finnish than Welsh - Tolkien was fascinated by the Kalevala.

Player Freewoman, Tolkien grew up fascinated with the Welsh words on train cars. It resulted in his becoming a linguist and lexicographer for the Oxford English Dictionary ("wasp" is one word he traced to its roots). Tolkien invented several languages for Middle Earth, and would occasionally write to his son, dismayed that he had discovered a verb that was conjugated improperly!

I looked it up; apparently Sindarin is indeed based on Welsh but Quenya is based on Finnish, if that clears it up.

I used a life, I love Tolkien and know he was a professor of language I thought it was Finnish and that he’d based a lot of his languages around Scandinavian. Whatever he used he created one of the most vibrant and colourful worlds ever to appear in literature and his characters will be remembered by all who have read his works or have seen the films, can’t wait to see the second season of Rings of Power!

BeamingSwan222, looks like the question needs amendment lol!

Player Freewoman, My mother was born in Wales and so in know a bit of this language. Don't recall hearing it in the film's.

pretty sure Tolkien based elvish language on finnish after reading Kalevala

Sindarin is based on Finnish. Some of the words are basically Finnish words with a letter taken off the end.

BeamingSwan222, agreed