Piping is divided into three major categories:
Large bore pipe generally includes piping which is greater than two inches in diameter.
Small bore pipe generally includes piping which is two inches and smaller in diameter.
Tubing is supplied in sizes up to four inches in diameter but has a wall thickness less than that of either large bore or small bore piping and is typically joined by compression fittings.
Within industry, piping is a system of pipes used to convey fluids (liquids and gases) from one location to another. The engineering discipline of piping design studies for efficient transport of fluid is called Piping Engineering.