The main cities that serve as the centers of government for countries or regions; or large uppercase letters used at the beginning of sentences and names.
From Latin 'capitalis' (of the head) from 'caput' (head). When referring to cities, 'capital' means the 'head' city where government authority sits; when referring to letters, it comes from the capital letters used in Roman inscriptions.
It's wild that the same word means both 'the city where government happens' and 'the big letters we use' because both originally meant 'the head' or 'chief'—the capital is where the chief ruler lives, and capital letters are the chief form of letters.
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