Autocracy
Etymology
From Greek autokráteia, from autós ("self") and krátos ("power, strength"): power held in and by oneself, answerable to no other. It was a formal title of the Russian tsars, styled autocrats, before broadening into the general term for one-person rule. The self- in the root is the whole point: the ruler is the source of authority, not its servant.
noun · /aw-TOK-ruh-see/
A system of government in which one person holds unlimited power, unchecked by law or institutions.
What it names
It strips away the ceremony to name the core fact of a regime — that final authority collapses into a single will.
Example
Each emergency decree chipped away at the courts until the presidency had hardened into an autocracy.
Related idea
Autarky looks and sounds similar but is unrelated — it means economic self-sufficiency, built on Greek arkeîn, "to suffice," not krátos, "power." An autocracy concentrates rule; an autarky seeks to need no one.