# 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.

**Structure**: a **structure** is that which permitting **Similarity** to other **Similars**. **Example**: **Circular** is a structure since it permits **similarity** **to** anything that is **round**. **Example**: **Red** is a structure since it permits **similarity to** anything that is **red**. **Example**: **Numeral** is a structure since it permits **similarity to** anything that is a **number**. ff calls a list e.g. **{1,2,3}** as a **structure**, or a function e.g. **cos\[ \]** a **structure** or an **algebraic structure** e.g. **x^2-1**.