Roots of a system which are trivial in nature because they arise from a definition or well known nature rather than the system's relationship. Ex 1: The one trivial root of x/2=sin(x) is at x=0 since sin(0)=0, but transcendental roots occur near x=+1.895... and x=-1.895...
Ex 2: The continuous definition of the Riemann zeta function has the reciprocal of Gamma(z) multiplied by a complex integral, and the nature of Gamma is well known at -2, -4, -6 ... to go to infinity, hence its reciprocal goes to zero and the Riemann Zeta function also does. These roots are trivial.