An adapter having standard pipe threads on one end or an unthreaded end designed to accommodate a pipe. The other end has external or internal machine threads (straight threads other than pipe or hose series) and is designed to facilitate a gasket, preformed packing, washer, or the like to form a seal at the boss. It is designed to join a pipe or pipe fitting to a boss or boss fitting in a straight line on items such as tanks, housing, valve fittings, or the like. See also adapter bushing and coupling, pipe.