What are short pieces of pipe threaded on both ends called?

Short pieces of pipe threaded on both ends are commonly referred to as "nipples." They are specifically designed to connect two other pieces of pipe or fittings together, allowing for a seamless transition in a piping system. Nipples come in various lengths, but regardless of length, the defining feature is their threading on both ends, which facilitates ease of installation and secure connections.

This terminology is essential in plumbing and pipefitting, as it distinguishes nipples from other components like adapters, which may serve different functions, or couplings, which usually connect two pipes or tubes that are not necessarily threaded. Fittings is a broader term that encompasses various components in piping systems, including elbows, tees, and others, highlighting the specificity of the term "nipples" in this context. Understanding these distinctions is crucial for effective communication and successful execution of plumbing tasks.