addition addition /əˈdɪʃən/

noun

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