Terminologies

lhs : Left Hand Side

rhs : Right Hand Side

p = q : an identity

Equational Expression: expr1 = expr2 e.g. expr1 = a*x+b and expr2 = cos[b-c]

copy: when an object is duplicated, byte by byte so to say, into a facsimile.

This definition of copy is the simplest to grasp the concept. In due places, more sophisticated definitions will be produced.