This article advocates a formal language approach for human resource development (HRD) theory building. To this end, it develops a theoretical framework for comparative HRD (CHRD) within the form of a formal language system. Through a review of existing HRD literature in comparative research, We generalize the research into three axioms of CHRD expressed to offer insight for future research in comparative realms with each axiom focusing on a particular comparative facet. Combining the axioms, we formally provide a definition of CHRD. We further derive implications for future HRD research and address related challenges in existing CHRD research.