In commutative algebra, a Rees decomposition is a way of writing a ring in terms of polynomial subrings. They were introduced by .
Suppose that a ring R is a quotient of a polynomial ring k[x<sub>1</sub>,...] over a field by some homogeneous ideal. A Rees decomposition of R is a representation of R as a direct sum (of vector spaces)
where each ÷<sub>ñ</sub> is a homogeneous element and the d elements ø<sub>i</sub> are a homogeneous system of parameters for R and ÷<sub>ñ</sub>k[ø<sub>f<sub>ñ</sub>+1</sub>,...,ø<sub>d</sub>] â k[ø<sub>1</sub>, ø<sub>f<sub>ñ</sub></sub>].