Tube vs. Pipe

While laypersons use the words interchangeably, in engineering a Tube is strictly differentiated from a Pipe.

 Tube: Measured by its exact Outside Diameter (OD) and precise Wall Thickness (gauge). Tubes are used for structural, mechanical, or medical applications where exact physical dimensions are critical.

Pipe: Measured by its internal capacity to transport fluids (Nominal Pipe Size).