A lens is a curved piece of glass or other transparent material that is used to refract light and form an image. The term 'lens, type of' can refer to four different types of lenses: trifocal (8 letters), toric (5 letters), convex (6 letters), and bifocal (7 letters). A trifocal lens is a lens with three distinct optical powers, allowing for clear vision at near, intermediate, and far distances. A toric lens is a lens with two distinct optical powers, allowing for clear vision at two different distances. A convex lens is a lens that is thicker in the middle than at the edges, and is used to focus light rays onto a single point. Finally, a bifocal lens is a lens with two distinct optical powers, allowing for clear vision at near and far distances.