Terylene and Orlon are classified as fibres due to their structural properties and usability in fabric production. Terylene, a type of polyester, is widely used for making textiles due to its strength, durability, and resistance to stretching. Orlon, a type of acrylic polymer, is also used as a fibre because of its wool-like texture and lightweight nature. Teflon and starch do not have fibre-forming characteristics, which makes them unsuitable in this context.