What is heat? Write $SI$ and $CGS$ unit of heat and give their relation.

(N/A) Heat is a form of energy that flows from a body at a higher temperature to a body at a lower temperature due to the temperature difference between them.
The $SI$ unit of heat is the Joule $(J)$.
The $CGS$ unit of heat is the calorie $(cal)$.
The relation between the $SI$ and $CGS$ units is: $1 \ cal = 4.184 \ J$ (often approximated as $4.2 \ J$).