Antonym of SYNTHETIC

Synthetic : (of a substance) made by chemical synthesis, especially to imitate a natural product.
Cosmetic : relating to treatment intended to restore or improve a person's appearance.
Plastic : a synthetic material made from a wide range of organic polymers such as polyethylene, PVC, nylon, etc., that can be moulded into shape while soft, and then set into a rigid or slightly elastic form.
Affable : friendly, good-natured, or easy to talk to.
Natural : existing in or derived from nature; not made or caused by humankind.

Antonym of Synthetic is Natural