Lanolin (from Latin lāna 'wool', and oleum 'oil'), also called wool yolk, wool wax, or wool grease, is a wax secreted by the sebaceous glands of wool-bearing animals. Lanolin used by humans comes from domestic sheep breeds that are raised specifically for their wool. Historically, many pharmacopoeias have referred to lanolin as wool fat (adeps lanae); however, as lanolin lacks glycerides (glycerol esters), it is not a true fat. Lanolin primarily consists of sterol esters instead. Lanolin's waterproofing property aids sheep in shedding water from their coats. Certain breeds of sheep produce large amounts of lanolin.