Pipe Nipple
The Pipe nipple is a short stub of a pipe that has a male pipe thread at each end or one end. It is used for connecting two other fittings. Nipples are used for connecting pipes, hoses, and valves. Pipe nipples are used in low-pressure piping.
Swage Nipple
The Swage Nipple is like reducers but small in size and used to connect pipes to smaller screwed or socket-welded pipes. Like reducers, they are also available in concentric & eccentric types. Swages are available in different end types. Such as both plain ends or one plain and one threaded end.