核心畫面
You can think of theirs as their plus the noun already folded inside it. Once everyone knows what you are talking about, you do not need to say the thing again — 'That car is theirs' already carries 'car' in it, so nothing comes after. It is the standing-alone form: it points at people you have already mentioned and says the thing belongs with them.
可以想成 theirs 就是 their 把後面那個名詞吞進肚子裡之後的樣子。話講到一半，大家已經知道在講什麼東西了…更多收起
可以想成 theirs 就是 their 把後面那個名詞吞進肚子裡之後的樣子。話講到一半，大家已經知道在講什麼東西了，就不必再說一次：That car is theirs 這句話裡，「車」已經藏在 theirs 裡面了，所以它後面不再接名詞。一種想法是：their 要牽著一個名詞才站得住（their car），theirs 則是自己一個人站著，手往前面提過的那些人一指，說「那東西是跟他們一起的」。原始詞典資料2 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。
theirspron/ðɛəz/
- 1
That or those belonging to them; the possessive case of they, used without a following noun.
- This luggage is theirs. These passports are also theirs.
- Theirs cost a lot more than ours.
- 2
informalTheir house or home.
- Let's go over to theirs.
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。