Sindarin 

cin

pronoun. you (sg. fam.)

Sindarin Group: Eldamo - neologism/reconstructions. Published by

cên

gore

(i gên, o chên, construct cen) (wedge), pl. cîn (i chîn). Alternative sg. form cîn (i gîn, o chîn, construct cin), no distinct pl. form except with article (i chîn)  (VT45:20)