to break in指非法強行闖入或打斷(to enter illegally by force or to interrupt)
例如﹕
Someone broke in(或into) the store and stole some cash.
有人破門闖入店鋪，偷走一些現鈔。
Breaking into the banks seems uncommon in the small city.
在小城裡，盜竊銀行倒不常見。
It's impolite to break in(或into) someone's conversation without asking for permission.
未經許可而打斷別人說話，是不禮貌的。
也可當名詞﹕
There were two break-ins at restaurants during last week.
上周餐館發生兩次竊盜。
但to break down是指機器壞了(mechanical malfunction)
例如﹕
Unexpectedly, the bus broke down on its way to school yesterday.
不料，公車昨天開去學校途中出現故障。
也當名詞用﹕
There was a washer break-down, so she had to wash her clothes by hands.
洗衣機壤了，她只好用手洗衣服。
有時當形容詞﹕
Most broken-down cars would be towed at the owners' expenses.
汽車出現機械故障，多半需要主人花錢拖走。
(4)to carry out與to carry on:
to carry out是指執行(to perform or to fulfill)
(多半指某件事情)
例如﹕
Our new boss is trying to carry out his don't-ask-don't-tell policy.
我們新老闆想要執行他的「不問不說」政策。
Actually, we all should have carried out our obligations and duties without any complaints.
實際上，我們都要毫無怨言地履行我們的義務與責任。
China's carrying out its peaceful foreign policy seems to be convincing to the world.
中國實行和平外交政策對世界似乎有說服力。
To carry out your current promises to your girlfriend is important for your lifelong commitment.
為女友實現目前的諾言，對履行你一生所要承擔的義務很重要。
但to carry on是繼續或保持的意思(to continue or to maintain)(後面多指事物)
例如﹕
Mr. A indicated(that) he would not carry on his father's retail business.
A先生表示不願繼承他老爸的零售生意。
The two old women have been carrying on gossiping for hours.
兩位老婦人繼續瞎扯了幾個小時。
有時也當名詞用﹕
How many carry-ons are the passengers allowed to bring on the airplane?
旅客可以帶幾件手提行李上飛機?
(5)to check in與to check up:
to check in是指登記(to register)
例如﹕
As soon as our airplane arrives, we have to check in at the Customs Office.
一旦飛機到達，我們就要到海關登記。
Mr. A goes to the library regularly; he always remembers to check in and check out his books.
A先生經常去圖書館；他都記得還書和借書。
(check out是check in的反義字)
Having checked in at the hotel, Ed played a slot machine at the casino.
Ed在旅館登記後，就到賭場玩吃角子老虎機。
也當名詞用﹕
There is always a check-in desk when you enter a hotel.
當你走進旅館，都有一個登記服務台。
I would like to know your library check-out policy.
我想知道你們圖書館的借書規則。
(以上check-in和check-out都是名詞，修飾另一名詞desk和policy)
但to check up是檢查或調查(to examine or to investigate)
例如﹕
The 80-year-old man checked up on his vision for driving.
八十歲男子為駕車而檢查視力。
There may be some discrepancies in the billing; you'd better check up on it.
帳單裡大概有錯，你最好檢查一下。(it指billing)
Being under suspicion for stealing goods, the man was checked up on by the police.
警察調查這位男子，懷疑其偷竊貨物。
也可當名詞﹕
To all retirees, a regular physical check-up seems necessary.
所有退休人員最好定期體檢。
