  For the purpose of applying laws or principles originated from thermal
systems to granular athermal systems, we may need to properly define the
critical temperature concept in granular powders. The conventional
environmental temperature in thermal systems is too weak to drive movements of
particles in granular powders and cannot function as a thermal energy
indicator. For maintaining the same functionality as in thermal systems, the
temperature in granular powders is defined analogously and uniformly in this
article. The newly defined granular temperature is utilized to describe and
explain one of the most important phenomena observed in granular powders, the
jamming transition, by introducing jamming temperature and jamming volume
fraction concepts. The predictions from the equations of the jamming volume
fractions for several cases like granular powders under shear or vibration are
in line with experimental observations and empirical solutions in powder
handlings. The goal of this article is to establish similar concepts in
granular powders, allowing granular powders to be described with common laws or
principles we are familiar with in thermal systems. Our intention is to build a
bridge between thermal systems and granular powders to account for many
similarities already found between these two systems.
