A set 
of all polynomials in 
variables, 
, ..., 
such that if 
, 
,
and 
are members, then so are 
and 
,
where 
is any polynomial in 
, ..., 
.
Modular System
See also
Hilbert's Theorem, Module, Modular System BasisExplore with Wolfram|Alpha
Cite this as:
Weisstein, Eric W. "Modular System." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/ModularSystem.html