What does ADDITION mean?

noun

1. a component that is added to something to improve it“the addition of a bathroom was a major improvement”
2. the act of adding one thing to another“the addition of flowers created a pleasing effect”
3. a quantity that is added“there was an addition to property taxes this year”
4. something added to what you already have“the librarian shelved the new accessions”
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”