An Etymological Dictionary of Astronomy and Astrophysics

1. Math.: A number or letter placed before an algebraic expression to indicate that the expression is to be multiplied by that factor, e.g. in the expression 2 x³, 2 is the coefficient of x³. In general, any factor of a product is called the coefficient of the product of the remaining factors.
   

2. Physics: Factor which measures some specified property of a given substance, and is constant for that substance under given conditions, such as the coefficient of friction. → factor.

Etymology (PE): Hamgar, from ham- “together,” → com- + -gar agent suffix, from kar-, kardan “to do, to make,” Mid.Pers. kardan, O.Pers./Av. kar- “to do, make, build,” Av. kərənaoiti “makes,” cf. Skt. kr- “to do, to make,” krnoti “makes,” karma “act, deed;” PIE base k^wer- “to do, to make.”