Pilling is the small, fuzzy balls of fibre that build up on a fabric's surface after friction from everyday sitting, cushions rubbing together or clothing brushing against the weave. It happens when short, loose fibres work free from the yarn and tangle together rather than shedding away completely.
Some fibres, particularly certain synthetics and loosely spun wools, pill more readily than tightly woven natural fibres. A fabric shaver or a fine toothed comb can remove pills without damaging the weave underneath, and a Martindale rating alone will not tell you how much a specific fabric will pill, so it is worth checking reviews or samples. See our sofa fabrics guide for fibres that resist pilling.