金庫（きんこ、kinko）
- safe (box)

The Japanese word 金庫 （きんこ） primarily means "safe," "strongbox," or "vault." It refers to a secure container used to store valuables such as money, important documents, jewelry, and other items that need protection from theft, fire, or other hazards. The word 金庫 can describe everything from a small, home-use safe to a large, industrial vault.

⚫︎金庫にお金を入れる。 Translation: I put money in the safe. ⚫︎あの会社は大きな金庫を持っている。 Translation: That company has a large vault. ⚫︎この金庫の暗証番号を忘れてしまった。 Translation: I forgot the combination to this safe.

You use 金庫 when talking about places or containers designed for secure storage. It's used in various contexts, from personal security to business operations. You would use it to describe where something valuable is kept or to discuss the act of securing something within a safe.

The word 金庫 is typically written with the kanji 金 (kin - gold, money) and 庫 (ko - storehouse, warehouse). The reading is きんこ in hiragana. There are no other common ways to write this word, nor are there significant variations in the okurigana.

⚫︎保管庫（ほかんこ） - Storage vault (often used for more general storage purposes) ⚫︎セーフ（seefu) - safe (loanword) ⚫︎ロッカー（rokkaa）- locker (can sometimes be used for storing valuables, but less secure than a 金庫.)

There aren't direct antonyms for 金庫, as the concept of "not a safe" doesn't have a specific single-word opposite. However, the opposite of the function of 金庫 might be considered: ⚫︎露出（ろしゅつ） - exposure/being exposed. ⚫︎開放（かいほう） - openness/being open.

銀行の金庫には、たくさんのお金が保管されている。 ・Translation: A lot of money is stored in the bank's vault. ・Explanation: This sentence describes the typical contents and function of a bank's 金庫.

大切な書類は金庫に入れて、厳重に保管してください。 ・Translation: Please put important documents in the safe and keep them securely. ・Explanation: This sentence gives instructions on how to secure important documents using a 金庫.

The word 金庫 is a compound word formed from 金（kin - gold, or more broadly, money/valuable things） and 庫（ko - storehouse, warehouse）. Therefore, the literal meaning of 金庫 is a "storehouse for valuables" or a "money storehouse," reflecting its function as a secure place for keeping valuable items.