Definition of addition noun from the Oxford Advanced American Dictionary

Oxford3000

addition

noun
/əˈdɪʃn/
 
 
1 [uncountable] the process of adding two or more numbers together to find their totalchildren learning addition and subtraction antonym subtraction at subtract2 [countable] addition (to something) a thing that is added to something elsethe latest addition to our line of carsan addition to the family (= another child)last-minute additions to the government's package of proposals3 [uncountable] addition (of something) the act of adding something to something elsePasta's basic ingredients are flour and water, sometimes with the addition of eggs or oil.4 [countable] addition (to something) a new part that is added to a buildingarchitects who specialize in home additionsThe addition should match the architecture of the house.IDIOM

in addition (to someone/something)

used when you want to mention another person or thing after something else
In addition to these arrangements, extra ambulances will be on duty until midnight.There is, in addition, one further point to make.in additionin addition to
Usage noteUsage note: additionadding another itemBilingual children do better on IQ tests than children who speak only one language.In addition/What is more, they seem to find it easier to learn third, or even fourth, languages.Learning another language not only improves children's job prospects in later life, but also boosts their self-esteem.Teaching children a second language improves their job prospects in later life.Other benefits include increased self-esteem and greater tolerance of other cultures.Another/One further/One additional reason for encouraging bilingual education is that it boosts children's self-esteem.Studies suggest that bilingual children find it easier to learn additional languages. There is, moreover, increasing evidence that bilingual children perform better across a range of school subjects, not just foreign languages.His claim that children find bilingual education confusing is based on very little evidence.Moreover, the evidence he does provide is seriously flawed.Research has shown that first-language development is not impeded by exposure to a second language.Furthermore, there is no evidence to support the claim that children find bilingual education confusing.