Pheromones are chemical substances that are secreted by an animal and that affect the behavior or physiology of another individual of the same species. Pheromones are used for a variety of purposes, including communication, attraction, and territorial marking.

Examples of pheromones include:

* The sex pheromone of the moth _Bombyx mori_, which is used to attract mates

* The alarm pheromone of the ant _Atta sexdens_, which is used to warn other ants of danger

* The territorial pheromone of the lion _Panthera leo_, which is used to mark territory and deter other lions

Pheromones are typically airborne, but they can also be transmitted through contact or by direct injection. Some pheromones are even detectable by humans, such as the scent of mothballs or the odor of fresh urine.

The study of pheromones is called pheromonology.