Open English Wordnet
Nouns
(n)addition, add-on, improvera 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” (n)additionthe act of adding one thing to another“the addition of flowers created a pleasing effect”,
“the addition of a leap day every four years” (n)addition, increase, gaina 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” (n)accession, additionsomething added to what you already have“the librarian shelved the new accessions”,
“he was a new addition to the staff” (n)additiona suburban area laid out in streets and lots for a future residential area (n)summation, additionthe arithmetic operation of summing; calculating the sum of two or more numbers“the summation of four and three gives seven”