An ex officio member is a member of a body (a board, committee, council, etc.) who is part of it by virtue of holding another office. The term is Latin, meaning literally "from the office", and the sense intended is "by right of office"; its use dates back to the Roman Republic.
A common misconception is that the participatory rights of ex officio members are limited by their status. This is incorrect, although their rights may be indeed limited by the by-laws, guidelines or rules of a particular body.
There may be voting and non voting members. Or the vote may not be collective but the result of a votive act.