signature

signature 1 The part of the prescription that contains the physician’s directions to the patient. For example, the signature might say “take twice daily with food.” Also known as sig. 2 The outward appearance of a natural object, which was once taken as a token of its special properties. For example, this ancient doctrine of signatures led some to conclude that the walnut, which looks something like a tiny brain, could be used to heal brain problems; the liverwort plant, which has a three-lobed liver-like leaf, was useful in treating liver disease; and so on.