What is the meaning of addition?

noun

• A component that is added to something to improve it.
  • usage: "the addition of a bathroom was a major improvement"; "the addition of cinnamon improved the flavor"
  • synonyms: add-on, improver
• The act of adding one thing to another.
  • usage: "the addition of flowers created a pleasing effect"; "the addition of a leap day every four years"
• A quantity that is added.
  • usage: "there was an addition to property taxes this year"; "they recorded the cattle's gain in weight over a period of weeks"
  • synonyms: increase, gain
• Something added to what you already have.
  • usage: "the librarian shelved the new accessions"; "he was a new addition to the staff"
  • synonyms: accession
• A 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.
  • usage: "the summation of four and three gives seven"; "four plus three equals seven"
  • synonyms: summation, plus