Licking is the action of passing the tongue over a surface, typically either to deposit saliva onto the surface or to collect liquid onto the tongue for ingestion or to provide pleasure to the genetailia. Many animals both groom themselves and drink by licking.

Licking in animals

Mammals typically lick their offspring clean immediately after birth; in many species this is necessary to free the newborn from the amniotic sac. The licking not only cleans and dries the offspring's fur, but also stimulates its breathing and digestive processes.

Some animals, such as cats, also use licking to cool themselves. As cats do not sweat the way humans do, the saliva deposited by licking provides a similar means of evaporative cooling

Many animals also drink by licking. While young mammals drink milk from their mothers' nipples by sucking, the typical method of drinking for adult mammals involves dipping the tongue repeatedly into water and using it to scoop water into the mouth. This method of drinking relies in part on the water adhering to the surface of the tongue and in part on muscular control of the tongue to form it into a spoonlike shape.

Hummingbirds are often said to "sip" nectar, but in fact they lap up nectar on their long tongues. Their tongues have fringed edges, which help in both nectar eating and in catching tiny insects. Mother hummingbirds also lick their chicks after a rainstorm to dry them by licking water droplets from the coats of the chicks to avoid chill.

Animals also use their tongue to enhance their sense of smell. By licking a surface, molecules on it are transferred via the tongue to the olfactory receptors in the nose and in the vomeronasal organ.

Dogs and cats use licking both to clean, and to show affection among themselves or to humans typically licking their faces..

Licking in humans

Compared to most other mammals, licking has a relatively minor role for humans. The human tongue (primarily used for speech) is relatively short and inflexible, and is not well adapted for either grooming or drinking. Instead, humans prefer to wash themselves using their hands and drink by sucking fluid into their mouth. Humans have much less hair over their skin than most other mammals, and much of that hair is in places which they cannot reach with their own mouth. The presence of sweat glands all over the human body makes licking as a cooling method unnecessary.

Nonetheless, licking does play a role for humans. Even though humans cannot effectively drink water by licking, the human tongue is quite sufficient for licking more viscous fluids. The practice of licking dishware and cutlery clean, though often considered uncivilized, is nonetheless quite common. Some foods are sold in a form intended to be consumed mainly by licking, e.g. an ice cream cone and a lollipop.