protagonist
the first actor
Today this word meansThe central figure of a story.
Prōtos (first) + agōnistēs (contender) — the "first actor."
Until Aeschylus raised the count to two and Sophocles to three, there was only one actor on stage.
The second actor was the deuteragonist, the third the tritagonist.
Worth noting
It does not mean "the good hero." Nor is its opposite, antagonist, a villain — merely "the one who contends against."