What is the difference between Pipe and Tube ?

People use the words pipe and tube interchangeably, and they think that both are the same. However, there are significant differences between pipe and tube.
The short answer is: A PIPE is a round tubular to distribute fluids and gases, designated by a nominal pipe size (NPS or DN) that represents a rough indication of the pipe conveyance capacity; a TUBE is a round, rectangular, squared or oval hollow section measured by outside diameter (OD) and wall thickness (WT), expressed in inches or millimeters.

SS pipes

CS Pipes

Alloys Pipes

Stainless Steel Pipes & Tubes Specifications