IPA: //ˈbɜːrθraɪt//
KK: /ˈbɜrθraɪt/
A right or privilege that someone has from birth, often related to family or heritage.
He believed that his title to the estate was his birthright.
Birthright → It is formed from "birth" (from Old English "berþ", meaning the act of being born) and "right" (from Old English "riht", meaning just or lawful). The word "birthright" refers to a right or privilege that one is entitled to by virtue of being born into a particular family or status.
Think of the 'act of being born' ('birth') giving you a 'just or lawful' claim ('right') to something — that's what a birthright means.