A casual event where an institution is open for inspection by anyone interested.

plural of open wound

plural of open water

An adoption in which the biological mother/biological parents and the adoptive family know each other's identities, and choose to remain in contact after the adoption process is finalized.

plural of open adoption

an incomplete electrical circuit through which no current can flow

plural of open circuit

(rare, mathematics, of a set) Being the interior of its closure.

A place of employment in which employment is in no way contingent on membership in a union, though a union may be the exclusive bargaining agent of the employees.

(religion) The practice of some Protestant churches to allow all people to take Communion, regardless of being members of the church or not.