Varna by worth and caste by birth are antithetical systems, not synonyms

Evidence

Varna and caste are two very different concepts. Varna is based on the principle of each according to his worth, while caste is based on the principle of each according to his birth. The two are as distinct as chalk is from cheese. In fact, there is an antithesis between the two. If the Mahatma believes, as he does, in everyone following his or her ancestral calling, then most certainly he is advocating the caste system, and in calling it the varna system he is not only guilty of terminological inexactitude, but he is causing confusion worse confounded. — Ambedkar, B R, Annihilation of Caste_ The Annotated…, 1258

Categorization

• DEFINE: The core analytic distinction of the chapter: worth vs birth as the two rival organizing principles.
• DEEPTHINKING: This ‘worth vs birth’ antithesis is a paradigm-level framing of how a reformist mislabel (varna) can smuggle in the very system it claims to replace.