is the wife of an earl a countess
The wife of a substantive peer is legally entitled to the privileges of peerage: she is said to have a ``life estate'' in her husband's dignity. Thus a duke's wife is titled a ``duchess'', a marquess's wife a ``marchioness'', an earl's wife a ``countess'', a viscount's wife a ``viscountess'' and a baron's wife a ``baroness''. Despite being referred to as a ``peeress'', she is not a peer in her own right: this is a 'style' and not a substantive title. However, this is considered a legal title, unlike the social titles of a peer's children.
Courtesy titles in the United Kingdom