Meaning of ADDITION in English

ad ‧ di ‧ tion S3 W1 /əˈdɪʃ ə n/ BrE AmE noun

[ Word Family: noun : ↑ addition , ↑ additive ; adjective : additonal, ↑ added ; verb : ↑ add ; adverb : ↑ additionally ]

1 . in addition used to add another piece of information to what you have just said:

The company provides cheap Internet access. In addition, it makes shareware freely available.

in addition to something

In addition to his movie work, Redford is known as a champion of environmental causes.

2 . [uncountable] the act of adding something to something else

the addition of something

The addition of networking facilities will greatly enhance the system.

with the addition of something

Turn sparkling wine into Buck’s Fizz with the addition of chilled orange juice.

3 . [countable] something that is added to something else, often in order to improve it

addition to

This excellent book will be a welcome addition to the library of any student.

latest/new/recent addition

the latest addition to our designer range

4 . [uncountable] the process of adding numbers or amounts to make a total ⇨ subtraction

5 . [countable] American English an extra room that is added to a building:

They built a big addition onto the back of the house.

Longman Dictionary of Contemporary English.      Longman - Словарь современного английского языка.