Monofilament thread, also known as invisible nylon, is exactly what its name says - a thread that has a single filament. Monofilament thread is the first choice for sewing "invisible" stitches.

It helps them to blend in with the fabric that you are sewing. This makes monofilament thread an excellent choice for blind stitching, and making exposed stitches or seams as "invisible" as possible. It is also a good alternative if you cannot find a thread color that matches your fabric. Monofilament thread looks and feels like fishing line, but it is too prone to tangling on reels.