Picture one seat and two : A steps up, then B, then A again, back and forth. What matters is not that there are two things, but that only one is up at a time and they swap in order. Day and night, black-and-white tiles, a shift roster of Mon-Wed-Fri against Tue-Thu — same movement, different shapes. And because there is always the other one waiting at the side, the word also came to point at the one kept ready in reserve.
From the word’s history
From Latin alternare 'to do first one thing then the other', from alternus 'one after the other, in turns', ultimately from alter 'the other (of two)'. The whole word is built on 'the other one' — which is why it covers both taking turns and the stand-in kept ready.
來自拉丁文 alternare（先做這個、再做那個），源自 alternus（一個接一個、輪流），最終來自 alter＝「兩個裡的另一個」。整個字都建在「另一個」上面：輪流是「換另一個上」，候補是「另一個在旁邊等著」——這也是為什麼「隔天一次」和「替補球員」看起來無關，其實同源。
Etymonline, https://www.etymonline.com/word/alternate
登入就可以看每一支怎麼連回核心畫面。
原始詞典資料13 筆記錄
以下是外部詞典記錄的用法，摘錄並精簡格式，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。
alternateadj/ɒlˈtɜː(ɹ).nət/
- 1
Happening by turns; one following the other in succession of time or place; first one and then the other (repeatedly).
- And bid alternate passions fall and rise
- One of the two boxes displaced by the new Pelaw installation will be Springwell, between Boldon Colliery and Pelaw, which has recently had the distinction of being manned by a husband and wife on alternate shifts.
- 2
governmentheraldryhobbiesHappening by turns; one following the other in succession of time or place; first one and then the other (repeatedly).
- Goldschmidt (Austria; creation July 27, 1862): [...] party, argent and gules, an eagle of alternate colors, [...]
- 3
mathematicssciencesDesignating the members in a series, which regularly intervene between the members of another series, as the odd or even numbers of the numerals; every other; every second.
- the alternate members 1, 3, 5, 7, etc.
- 4
Other; alternative.
- Hyperlinked text is displayed in alternate color in a Web browser.
- He lives in an alternate universe and an alternate reality.
- 5
biologybotanynatural-sciencesDistributed singly at different heights of the stem, and at equal intervals as respects angular divergence
- Many trees have alternate leaf arrangement (e.g. birch, oak and mulberry).
alternatenoun/ɒlˈtɜː(ɹ).nət/
- 1
That which alternates with something else; vicissitude.
- Grateful alternates of substantial peace.
- 2
A substitute; an alternative; one designated to take the place of another, if necessary, in performing some duty.
- An alternate for the first-string quarterback played the entire first half.
- Corridors beyond this point have collapsed. I'm looking for an alternate. Careful.
- 3
mathematicssciencesA proportion derived from another proportion by interchanging the means.
- 4
A replacement of equal or greater value or function.
alternateverb/ˈɒl.tə(ɹ)ˌneɪt/
- 1
To perform by turns, or in succession; to cause to succeed by turns; to interchange regularly.
- The most high God, in all things appertaining unto this life, for sundry wise ends alternates the disposition of good and evil.
- 2
To happen, succeed, or act by turns; to follow reciprocally in place or time; followed by with.
- The flood and ebb tides alternate with each other.
- 3
To vary by turns.
- The land alternates between rocky hills and sandy plains.
- 4
geometrymathematicssciencesTo perform an alternation (removal of alternate vertices) on (a polytope or tessellation); to remove vertices (from a face or edge) as part of an alternation.
- This case suggests that the alternation of a polyhedron should be bounded by actual vertex figures and alternated faces. The case of the cube is in agreement with this notion, since the alternated square is nothing.
摘錄自 英文維基詞典 English Wiktionary，已精簡格式；依 CC BY-SA 4.0 授權使用，改動後的內容同樣以此授權提供。