MI5 is a secret British government service whose job is to keep Britain safe from enemies already inside the country — foreign spies, terrorist plans, and people trying to hurt the UK from within.

MI5MI5(軍情五處) is a secret British government service是英國政府的一個秘密機關 whose job is to keep Britain safe from enemies already inside the country工作是保護英國不受已經潛入國內的敵人傷害 — foreign spies, terrorist plans, and people trying to hurt the UK from within像是外國間諜、恐怖攻擊計畫，還有想從內部傷害英國的人。

The letters stand for Military Intelligence, Section Five: an old army office-name that stuck, though actually the people who work there are not ordinary soldiers in uniform, and they are not the police either. Their work is inward: Britain itself.

The letters這幾個字母 stand for Military Intelligence, Section Five代表Military Intelligence, Section Five（軍事情報五處）: an old army office-name that stuck是一個沿用下來的舊軍方單位名稱, though actually the people who work there are not ordinary soldiers in uniform不過其實在裡面工作的人並不是穿制服的普通軍人, and they are not the police either也不是警察。Their work is inward他們的工作對象是對內的: Britain itself就是英國本身。

MI6 does a similar secret job, but in other countries. British newspapers say MI5 a little the way American papers say the FBI — a short, serious name for the home security service. The comparison is only a teaching picture; the two are not the same office.

MI6MI6(軍情六處) does a similar secret job做的是類似的秘密工作, but in other countries不過是在其他國家。British newspapers say MI5英國報紙提到MI5的方式 a little the way American papers say the FBI有點像美國報紙提到FBI一樣 — a short, serious name for the home security service都是給國內安全機關的一個簡短又正式的稱呼。The comparison這個對照 is only a teaching picture只是幫助理解用的說法; the two are not the same office兩者並不是同一個機關。

In speech we say each piece: M-I-five. The word intelligence here does not mean “clever”. It means secret information about danger.

In speech說出來的時候 we say each piece我們會一個一個字母說: M-I-fiveM-I-five。The word intelligence here這裡的intelligence一字 does not mean 'clever'不是「聰明」的意思。It means secret information about danger它指的是關於危險的秘密情報。

You meet MI5 in news, in spy stories, and in history; the tone is official, not playful.

You meet MI5你會在 in news, in spy stories, and in history新聞、間諜故事，還有歷史裡遇到MI5; the tone is official, not playful語氣是正式的，不是輕鬆好玩的。