Meaning of ADDITION in English

[noun]Twice a week the children are tested in basic mathematical skills such as addition (= calculating the total of different numbers put together) and subtraction. [U]Most working environments are improved by the addition of (= adding) a few plants and pictures. [U]A secretary would be a welcome/useful addition to our staff. [C]In addition to teaching, she also works in the holidays as a nurse. [U]In addition to his flat in London, he has a villa in Italy and a castle in Scotland. [U](humorous) I hear you're expecting a small addition to the family (= you are going to have a baby)! [C]

Cambridge English vocab.      Кембриджский английский словарь.