What term is used for short sections of pipe that are threaded on both ends?

The term used for short sections of pipe that are threaded on both ends is "nipples." Nipples are specifically designed to connect two other fittings or lengths of pipe together, typically allowing for a connection in plumbing or piping systems. Their threaded ends facilitate easy installation and disassembly, which is critical in applications where maintenance or adjustments might be needed.

Fittings broadly refer to various connections and components in plumbing systems but do not specifically denote the threaded nature or length characteristic of nipples. Couplings are used to connect two similar types of pipe or fittings, but they are usually not short sections with both ends threaded; they can vary in design and purpose. Adapters serve a different function of connecting pipes of different sizes or types, which isn't directly related to the characteristics described for nipples. Thus, the usage of "nipples" accurately captures the specific requirement of being short and threaded on both ends.