自己會變，所以說不準
指針自己在動，沒人碰它——這是核心畫面最直接的一面：變化不受你控制，於是產生了不確定。
changeable · adjective · C1
Likely to change often, especially amounts, prices, speeds, or temperatures, so you cannot be sure what they will be.
多變的
核心畫面
Think of a needle on a dial that will not settle — it drifts up, drops back, moves again. The thing is not fixed at one value; it is the kind of thing that takes different values.
一根不肯停下來的指針：溫度計、風速表、油價的線——它往上飄一點，又掉回來，再動一次。這個字講的不是「現在是多少」，而…更多收起
一根不肯停下來的指針：溫度計、風速表、油價的線——它往上飄一點，又掉回來，再動一次。這個字講的不是「現在是多少」，而是「這種東西本來就會落在不同的數值上」。所以它同時帶著兩種味道：一種是你無法預測（風向多變），一種是它可以被調到不同位置（火力可調）——兩者共用同一個畫面，差別只在動的是它自己，還是你在動它。From the word’s history
From Latin variare 'to change', from varius 'diverse, spotted, various', plus -able: 'able to vary'. The -able ending is why the word names a capacity, not an event — something that can take different values, whether or not it is changing right now.
這個字是 vary（變化，源自拉丁文 variare「使不同」、varius「各種各樣的」）加上 -able（能夠…的）。關鍵在 -able 這個尾巴：它說的是一種「能力」而不是一件正在發生的事。所以 variable 不是「正在變」，而是「屬於會變、能變的那一類」——這正好解釋了為什麼它既可以形容捉摸不定的天氣，也可以形容一個你自己轉得動的旋鈕。
Wiktionary (variable: Middle English, from Old French variable, from Latin variabilis / variare, from varius)
Three branches
可以被調成不同的值
一樣是「能落在不同數值上」的能力，只是主導權反過來：不是它自己飄，而是你把它調過去。所以這裡完全沒有不確定的味道，反而是一種好用的功能。
adjustable · adjective · C1
Able to be changed or set to different levels, such as speed or heat.
可調的
那個會變的東西本身
把形容詞變成名詞：不再說「這東西是多變的」，而是直接指著那個會變的項目——它是一個位置，等著被填入不同的值。
uncertain factor · noun · C1
Something that may be different in different situations, so you cannot be sure what will happen.
變數
原始詞典資料13 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。
variableadj[ˈvɛə.ɹi.ə.bl̩]
- 1
Able to vary or be varied.
- variable winds or seasons; a variable quantity; a variable resistor
- 2
Likely to vary.
- Lest that thy love prove likewise variable.
- 3
Marked by diversity or difference.
- 4
mathematicssciencesHaving no fixed quantitative value.
- 5
biologynatural-sciencesTending to deviate from a normal or recognized type.
variablenoun[ˈvɛə.ɹi.ə.bl̩]
- 1
Something that is variable.
- 2
Something whose value may be dictated or discovered.
- There are several variables to consider here.
- Bats host many high-profile viruses that can infect humans, including severe acute respiratory syndrome and Ebola. A recent study explored the ecological variables that may contribute to bats’ propensity to harbor such zoonotic diseases by comparing them with another order of common reservoir hosts: rodents.
- 3
mathematicssciencesA quantity that may assume any one of a set of values.
- 4
mathematicssciencesA symbol representing a variable.
- 5
computingengineeringmathematicsA named memory location in which a program can store intermediate results and from which it can read them.
- 6
astronomynatural-sciencesA variable star.
- 7
nauticaltransportA shifting wind, or one that varies in force.
- 8
nauticaltransportThose parts of the sea where a steady wind is not expected, especially the parts between the trade-wind belts.
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。