Hose is like flexible tubing, but it should generally be considered as PIPE.
Hose is sized by its Inside Diameter. (A notable exception to this is the case of FIRE HOSE, which is often sized by its O.D. due to its associated fitments, many of which use the O.D. as their determinant diameter.)
Hose is most typically (and traditionally) made of rubber, though modern technology has brought us myriad new materials suitable for various working fluids and physical working criteria.