What is "jonkheer"

Jonkheer (female equivalent: Jonkvrouw) is a Dutch honorific of nobility. In Belgium, the title of Écuyer (in French) or Jonkheer/Jonkvrouw (in Dutch) is the lowest title within the nobility system, recognised by the Court of Cassation. It is the cognate and equivalent of the German noble honorific Junker, which was historically used throughout the German-speaking part of Europe, and to some extent also within Scandinavia.