it is in the us customary unit or else we wouldnt be learning about. there for it is in the us customary unit.
US customary units
Fahrenheit is a customary unit
customary
The SI unit is a Newton. The old US unit is the pound-force or the poundal.
The customary unit of capacity for a bathtub is gallons.
It is a customary unit.
customary
It is a customary unit.
pound
A Customary Unit or non-SI unit is a measurement unit that is not part of the metric system. Customary units are mainly units of the Imperial system but they could be localised customary units - such as Gaj (for area) is South Asia.
It is the basic unit of time in both systems.