Fiber is an important part of a healthy diet, and can be found in many different forms. DIETARY fiber, with seven letters, is a type of carbohydrate that cannot be digested by the body, and is found in plant-based foods such as fruits, vegetables, and grains. OPTIC, with five letters, is related to vision and the transmission of light. BRAN, with four letters, is the outer layer of cereal grains, and is a good source of DIETARY fiber. Coir, with four letters, is a type of fiber made from coconut husks, and is often used in rope and mats. HEMP, with four letters, is a type of plant fiber used to make fabrics and paper. Istle, with five letters, is a type of fiber made from agave plants, and is used to make rope and twine. METTLE, with six letters, is a term used to describe courage and determination. Optics, with six letters, is the study of light and its properties. Roughe, with six letters, is a type of fabric with a rough texture. ROUGHAGE, with eight letters, is another term for DIETARY fiber.