Other forms: countesses
A countess is a noblewoman, equal in status to an earl or a count. Countesses either inherit the title when they're born or gain it by marrying a noble.
If a woman marries the Earl of Sandwich, she'll become a countess, although people directly addressing them will call them "Lord" and "Lady." Marrying a viscount or count is another way to gain the title of countess. The idea of such a title, and the word itself, may seem old-fashioned, but there are many countesses living today in England and Scotland. The word countess comes from count and its Latin root, comes, "companion to the emperor."