1.NounThe act, process, method, or an instance of representing by a system or set of marks, signs, figures, or characters.
2.NounA system of characters, symbols, or abbreviated expressions used in an art or science or in mathematics or logic to express technical facts or quantities.
"This section lists all algebraic notation used in this book.; The notations used in the two books differed."
3.NounA specific note or piece of information written in such a notation.