A leavening agent used in doughs and batters. It usually comes in a dry, bead like form (which can be compressed into cakes), although it also exists in a fresh form. It is best activated at a temperature of 110 degrees F to 115 degrees F (the temperature of a baby bottle or a comfortable bath). Anything too cold won't activate it, too hot will kill it.
Meaning of YEAST in English
English dictionary of cooking and food terms. Английский словарь терминов приготовления и условий питания. 2012