Noun
1. a component that is added to something to improve it;
"the addition of a bathroom was a major improvement""the addition of cinammon improved the flavor"2. the act of adding one thing to another;
"the addition of flowers created a pleasing effect""the addition of a leap day every four years"3. a quantity that is added;
"there was an addition to property taxes this year""they recorded the cattle's gain in weight over a period of weeks"4. something added to what you already have;
"the librarian shelved the new accessions""he was a new addition to the staff"5. a suburban area laid out in streets and lots for a future residential area
6. the arithmetic operation of summing; calculating the sum of two or more numbers;
"the summation of four and three gives seven""four plus three equals seven"