the.com/crown prince

means The male heir who is first in line to inherit the throne, by established right of succession rather than mere hope.

from A straightforward compound: 'crown' standing for the monarchy itself (the literal headpiece became shorthand for the whole office of ruling), plus 'prince,' from Latin princeps — 'first one,' from primus (first) and capere (to take or seize). So a prince was literally 'the one who takes first place.' 'Crown prince' as a fixed title spread through European royal houses to mark the heir apparent specifically, distinguishing him from other princes who were merely relatives, not destinies-in-waiting.