This chapter examines the following concepts: filaments, strands, tows, rovings, and yarns, woven and knitted fabrics (cloth), non-woven fabrics (mat), prepregs, braided, stitched, and three-dimensional laminates, performs, hybrids, and whiskers. Reinforcements are sold and used in composites in many different forms. Some of these forms are essentially available as produced by the fiber manufacturer. Others are converted into cloth, mat, or a variety of other forms. These technologies have been developed over the centuries by the textile industry and the composites industry has shared them. Still other forms have been developed specifically for use in composites. Fabric properties can depend upon a host of parameters including the following: type of weaves, areal weights, fabric thicknesses, thread counts, variety of fiber diameters, other fiber properties for both warp and fill, and directional breaking strengths. Materials that combine two or more types of reinforcements are called hybrids. The form in which the reinforcements are used makes a difference in the properties of the composite. The form also makes a difference in the methods of manufacturing. Therefore, examining the nature of the reinforcement is an important aspect ofunderstanding composites.