addition
noun
a component that is added to something to improve it
“the addition of a bathroom was a major improvement”
“the addition of cinnamon improved the flavor”
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”
Oppositessubtractiona 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”
something added to what you already have
“the librarian shelved the new accessions”
“he was a new addition to the staff”
Synonymsaccessiona suburban area laid out in streets and lots for a future residential area
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”
Source: WordNet 3.1, Princeton University