  There are some misnomers and misconceptions about what is heat and what is
work; the recognition of heat and work is even more difficult when it comes to
categorize energy as heat or work. Since both heat and work are energy the
name-confusion does not make much difference from engineering point of view,
but re-defining `heat' and `work' in the right-perspective of
second-law-of-thermodynamics \cite {ref1} is necessary to revise our
understanding at fundamental level. It is concluded that `heat is the energy
carried by mass-less \textit{photons} whereas work is energy carried by
mass-ive material \textit{fermions}'. Revised understanding of heat and work in
this way has far reaching consequences in Physics [2-4]. The present paper lays
emphasis on re-defining heat and work, removing the prevailing misconception,
talks about single photon interaction and heat property of photon. Also,
interestingly, it is noted that different fields of study such as
`Thermodynamics' and `Relativity' are interlinked.
