- 1在其中（正式用語，常見於法律文件）
"Therein" is a formal, old-fashioned word meaning "in that place" or "in that thing" (like inside a document). You mostly see it in legal writing, official documents, or very formal speech — for example, a contract might say "the rules therein," meaning "the rules inside that document." You would almost never hear it in normal daily conversation.
From the word’s history
From Middle English theryn, from Old English þǣrin; there + in.
源自古英文 þǣrin，就是 there 加上 in。
組成there + in — literally "in there."
原始詞典資料1 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。
thereinadv/ˈðɛəɹˈɪn/
- 1
in that; in that place; in him/her/it.
- September 1792, George Washington, letter My observation is that whenever one person is found adequate to the discharge of a duty... it is worse executed by two persons, and scarcely done at all if three or more are employed therein.
- "Ha," said Robin, "comest thou from Locksley Town? Well do I know that fair place for miles about, and well do I know each hedgerow and gentle pebbly stream, and even all the bright little fishes therein, for there I was born and bred. Now, where goest thou with thy meat, my fair friend?"
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。