IPA: /ˈbærənɪs/
KK: /ˈbɛrənɪs/
A woman who has the title of a baron, which is a rank of nobility. She may be the wife or widow of a baron, or she may hold the title herself.
The baroness hosted a grand dinner for the local nobility.
Baroness → The word is formed from "baron" (from Old French *baron*, meaning a nobleman or lord) and the suffix "-ess" (meaning a female). A baroness is a female member of the nobility, specifically the wife or widow of a baron.
Think of a 'baron' as a nobleman and the '-ess' indicating a female, so a baroness is a noblewoman.