We investigate the structure
of pure-syzygy modules in a pure-projective resolution of any right R-module
over an associative ring R with an identity element. We show that a right
R-module M is pure-projective if and only if there exists an integer n ≥ 0 and a
pure-exact sequence 0 → M → Pn→⋯→ P0→ M → 0 with pure-projective
modules Pn,…,P0. As a consequence we get the following version of a result in
Benson and Goodearl, 2000: A flat module M is projective if M admits an
exact sequence 0 → M → Fn→⋯→ F0→ M → 0 with projective modules
Fn,…,F0.