Alder is the common name of a genus of flowering plants (Alnus) belonging to the birch family Betulaceae. The genus comprises about 30 species of monoecious trees and shrubs, a few reaching a large size, distributed throughout the north temperate zone. The common name "alder" evolved from Old English "alor", which in turn is derived from Proto-Germanic root aliso. The generic name Alnus is the equivalent Latin name. Both the Latin and the Germanic words derive from the Proto-Indo-European root el-, meaning "red" or "brown", which is also a root for the English words "elk" and another tree: "elm", a tree distantly related to the alders.
The catkins of some alder species have a degree of edibility, and may be rich in protein. Reported to have a bitter and unpleasant taste, they are more useful for survival purposes. The wood of certain alder species is often used to smoke various food items, especially salmon and other seafood. Most of the pilings that form the foundation of Venice were made from alder trees. Alder bark contains the anti-inflammatory salicin, which is metabolized into salicylic acid in the body. Native Americans used red alder bark (Alnus rubra) to treat poison oak, insect bites, and skin irritations. Blackfeet Indians used an infusion made from the bark of red alder to treat lymphatic disorders and tuberculosis. Recent clinical studies have verified that red alder contains betulin and lupeol, compounds shown to be effective against a variety of tumors. The inner bark of the alder, as well as red osier dogwood, or chokecherry, was also used by Native Americans in their smoking mixtures, known as kinnikinnick, to improve the taste of the bearberry leaf. Alder is illustrated in the coat of arms for the Austrian town of Grossarl. Electric guitars, most notably the Fender Jazz Bass, Fender Precision Bass, Fender Stratocaster and Fender Telecaster, have been built with alder bodies since the 1950s. Alder is appreciated for its claimed tight and even balanced tone, especially when compared to mahogany, and has been adopted by many electric guitar manufacturers. As a hardwood, alder is used in making furniture, cabinets, and other woodworking products. For example, in the television series Northern Exposure 1992 season 3 episode "Things Become Extinct", Native American Ira Wingfeather makes duck flutes out of Alder tree branches while Ed Chigliak films.