| 1. | any shrub or tree belonging to the genus Alnus, of the birch family, growing in moist places in northern temperate or colder regions and having toothed, simple leaves and flowers in catkins. |
| 2. | any of various trees or shrubs resembling an alder. |
; akin to MHG alze < Gmc *al
sō, OHG elira, erila (G Erle) < Gmc *ális
, MLG els(e) < Gmc *alísō, hence Gmc *álus, alísō; cf. Pol olcha, Russ olʾkhá < IE dial. *alisā; Lith al̃ksnis, L alnus < IE dial. *alsnos
Alder Al·der (äl'dər), Kurt. 1902-1958.
German chemist. He shared a 1950 Nobel Prize for discoveries concerning the structure of organic matter.