Marquess (marquis in French) is a title of nobility in many countries in Europe. It is a rank higher than an earl but lower than a duke. 'Marquis' is correct in France, and 'Margrave' in Germany for a local ruler.
This title was usually granted by a monarch to reward a subject for longtime faithful service or some very notable deeds. The title is hereditary, meaning that is passes from a father to his eldest son. Usually if a man holding this title dies without having any male heirs, the title is said to become extinct, meaning that it is no longer held by anyone living.
The female equivalent of this title may be styled marquess. This rank may be held by the wife of a marquis or granted to a woman in her own right. A woman with the rank of marquess is called a marchionesse in the U.K. and elsewhere a marquise.