for a personal project, i'm searching for the sindarin word for the geometrical shape "diamond". i have yet to find it, or any other geometrical shape (square, triangle, etc.) has anyone any insight on this subject?.
Words for geometrical shapes
There is naith which Tolkien used both as "angle" and "triangle" from the root NEK "narrow". A clearer word for the triangle is nelthil (lit. "three-point(s)"), and based on that the square would be can(ad) + till, which can either be (old compound) *cannil or (new compound) *candil. Perhaps "turned square" could work as "diamond, lozenge", which I would translate as *perchandil, with the initial element *pern (cf. Q. querna "turned").
In other cases I also provide a more literal translation but I doubt that the Elves would call that particular shape a "diamond shape", but they could relate it to their heraldry. And perhaps "heraldry shape" can be translated as *tangant "token-shape".
Thanks, Elaran, your comment has certainly been helpful. I believe "perchandil" will work fine in the context I plan to use it for. Much obliged tips hat.