被加進來的那一個
既然 addition 是「加上去」，那被加上去的那樣東西，本身也可以叫 an addition——動作的結果，化成了一個具體的人或物。
something added to improve it · noun · B2
A thing that is added to something else, often to make it better.
新加入的人事物
核心畫面
You can picture the moment of joining: you take one thing and put it together with another, and now there is more than before. Everything else 'addition' means grows out of that simple act of one-more-on-top.
可以想成「把一個東西放到另一個東西旁邊、加上去」的那一刻：本來只有這些，現在多了一份。addition 的各種意思，…更多收起
可以想成「把一個東西放到另一個東西旁邊、加上去」的那一刻：本來只有這些，現在多了一份。addition 的各種意思，都是從這個「再添一個、變多了」的動作長出來的。From the picture
說話時再添一句
把「加上去」從實物搬到談話裡：講完一件事，再添一條訊息，就用 in addition 接上。
in addition · noun · B2
Used to bring in one more piece of information, on top of what you just said.
此外
Also in this word
the act of adding one thing to another · noun · B2
The act of putting one thing together with another thing.
加入
addition (arithmetic) · noun · B2
The math of putting numbers together to find a total.
加法
原始詞典資料7 筆記錄
以下是外部詞典記錄的用法，原文照列，我們還沒有寫成教學內容。上面的說明才是我們自己寫的；有些用法可能上面已經講過了。
additionnoun/əˈdɪʃ.ən/
- 1
The act of adding anything.
- The addition of five more items to the agenda will make the meeting unbearably long.
- 2
Anything that is added.
- 3
arithmeticThe arithmetic operation of adding.
- 4
entertainmentlifestylemusicA dot at the right side of a note as an indication that its sound is to be lengthened one half.
- 5
lawA title annexed to a person's name to identify him or her more precisely.
- […]They clip vs drunkards, and with Swiniſh phraſe / Soyle our addition, and indeede it takes / From our atchieuements, though perform’d at height / The pith and marrow of our attribute[…]
- 6
governmentheraldryhobbiesSomething added to a coat of arms, as a mark of honour.
- 7
chemistrynatural-sciencesorganic-chemistryan organic reaction where two or more molecules combine to form a larger one (the adduct).
資料來源：英文維基詞典 English Wiktionary（CC BY-SA 4.0）。 原文照列，未經改寫。