我們來看看一組問答以便理解：
What is the correct way to pluralize an acronym?
縮略詞複數形式的正確寫法是什麼？
For example, if I wanted to write the equivalent of
例如，如果我想寫與下面這句話等價的話，
There are many automated teller machines in this city.這城市裡有很多自動提款機。
Would it be
是應該寫成
There are many ATMs in this city.
or
還是
There are many ATM's in this city.
(could get confused with possessive form or contraction).
（會和所有格混淆，縮略語）
or just
還是簡單地這麼寫
There are many ATM in this city.
(assuming the final s is included in Machines represented by M).
（假定最後的s是包含在Machines 裡，由「M」這個詞來代表）
Maybe something else?
或者還有其他寫法？
……
回答是：
The Chicago Manual of Style has an interesting way to address this: They omit the apostrophe, unless there are periods in the abbreviation. So this would give you ATMs, or alternately A.T.M.'s. (A.T.M.s looks weird.)
《芝加哥格式手冊》中有一個有趣的方法來處理這種情況：他們一般省略掉單引號，除非這個縮略語中含有句點符號「.」。所以，對於你的問題，應該寫作ATMs，或者用另一種寫法 A.T.M.'s（而A.T.M.s看起來太奇怪了）
* 註：芝加哥格式是國外指導論文中引用條目時寫法的幾種規範之一。
Some web page indicates that acronyms ending in the letter "S" get an apostrophe, something I've seen before, but can't find in a general reference. So one would write ATMs and SOS's.
一些網頁上指出以「S」結尾的縮略語應該加上一個單引號，我看到過，但我找不到一個通用的參考。所以你應該寫ATMs 和SOS's。
This page on the North Carolina State University website references AP's rule as being to always use an apostrophe.
這個北卡州立大學的網站上引用了AP規則來指定縮略語的複數都要有一個單引號。
* 註：AP's rule指的是一種規範新聞中寫法的規約。
The 2009 AP Stylebook's "plurals" entry has no section on acronyms, but mentions "VIPs", I can't find anything addressing how to specifically pluralize acronyms. (The "abbreviations and acronyms" section is also of no help.)
2009年AP風格手冊中的「複數」一詞沒有提到縮略語的章節，但是提到過「VIPs」，我找不到如何處理特殊的縮略語複數形式的內容。（「縮寫和首字母縮略語」這一節也沒有幫助）
Personally, I omit using apostrophes unless I can't avoid it. I do use them when talking about single letters or where it would avoid confusion. (For example, SOs for "Significant Others" looks like an incorrectly capitalized SOS.)
我個人意見，除非無法避免的情況，我一般都省略掉單引號。在談及單個（大寫）字母時我使用（單引號），在可能必須用來避免混淆時（我也使用單引號）。（例如，「Significant Others」如果縮寫成「SOs」，會被人誤會成最後一個字母大小寫寫錯了的SOS）
現在，你會選擇哪一種寫法呢？