Definition of "Addition" :
noun: the act of adding one thing to another
"The addition of flowers created a pleasing effect."
noun: the arithmetic operation of summing; calculating the sum of two or more numbers
noun: a component that is added to something to improve it
"The addition of a bathroom was a major improvement."
noun: a suburban area laid out in streets and lots for a future residential area
noun: something added to what you already have
"He was a new addition to the staff."
noun: a quantity that is added
"There was an addition to property taxes this year."