Man-made materials as a group, especially cloth — nylon, polyester, acrylic, spandex and their relatives, all made by chemical processes rather than grown or taken from an animal. It is a plural noun and takes a plural verb: 'synthetics are cheaper', 'synthetics don't breathe well'. You meet it in the clothing trade, in care labels, in writing about sport gear and about the environment, and it is a handy word precisely because it saves you listing five fabrics. The word carries a mild everyday judgement in the world of clothes: 'I try to avoid synthetics' usually means 'I prefer cotton, wool and linen because they breathe' — a fair thing to say in a Taiwanese summer. But the trade itself is not so simple, since modern synthetics can beat natural fibres for warmth, weight and drying speed, which is why serious hiking clothes are almost entirely synthetic. Outside cloth, you will sometimes see the word for man-made substances generally, like synthetic rubber or synthetic oils, but fabric is the main home of it. Note that 'synthetic' by itself is the adjective; 'synthetics' is a noun meaning the things themselves.