Nj is a synonym of nanojoule.
As a letter nj
is a digraph from the letters n and j.
As a noun nanojoule is
As nouns the difference between energy and nanojoule
is that energy
is the impetus behind all motion and all activity while nanojoule
As nouns the difference between work and nanojoule
is that work
As a verb work
is to do a specific task by employing physical or mental powers.