IPA: /ˈɛə.ləs/
KK: /ˈɛrˌlɛs/
Describing a situation where a person does not have a successor or someone to inherit their property or title.
The king died heirless, leaving the throne without a rightful successor.
Heirless is formed from "heir" (from Old French *air*, meaning one who inherits) and "-less" (meaning without). The word "heirless" means without an heir or lacking someone to inherit.
Think of someone who is 'without' ('-less') an 'heir' — that's why heirless means lacking an heir.