QA
Quality Assurance is the sum total of the organised procedures ensuring that products will be fit for their intended use. Quality is ensured by GMP, GLP and other procedures operating in the R&D environment.

GMP
GMP is the part of Quality Assurance that ensures products are consistently manufactured to a standard appropriate to their intended use. It is concerned with both manufacturing and Quality Control procedures.

QC
Quality Control is the part of GMP which is concerned with sampling, specification and testing and also organization, documentation and release.