Estrane is a C18 steroid derivative, with a gonane core.
Estrenes are estrane derivatives that contain a double bond, with an example being nandrolone. Estratrienes (estrins) are estrane derivatives that contain three double bonds, for instance estrin (estra-1,3,5(10)-triene). A class of female sex hormones, estrogens, such as estradiol, estrone, and estriol are estratrienes.