“Slip” “Slip Socket” and “Socket” all
mean the same thing. The pipe glues into it. A ‘female’ end. The exception to
this is a “Slip T” in which case the “Slip part” slides over pvc pipe. It’s used
in construction projects as hinges or parts that need to move or slide.




“St” “Street” “Spg” and “Spigot” all
mean the same thing. It glues into another fittings socket. A ‘male’ end. Note:
There are both threaded street fittings and glue in street fittings. The street,
spigot, st or spg just refers to the mechanism, not whether it’s threaded or
glued in.




“MPT” and “MIPT” all
mean the same thing. Male Iron Pipe Thread. 




“FPT” “FIPT” all
mean the same thing. Female Iron Pipe Thread.




“NPT” means
National Pipe Thread. Sometimes you may see this as NIPT which is Nation Iron
Pipe Thread, however we don’t use it because it confuses people. They think the
fitting is made of iron when in fact it’s plastic. All fittings used to be iron
or steel, but most have been replaced with plastic or brass. But they still use
the same threads. Also you will see FNPT or MNPT or FNIPT or MNIPT. All of these
are referring to the same thing, just M=Male and F=Female.