Call in 作"請來"、"找來"、"召來"解，"請人來作某種專業(yè)的咨詢或幫忙"的意思。如：
Your father is ill, you should call in a doctor at once.
你父親病了，應該馬上去請個大夫來。
The police have been called in to help make it clear.
已請來了警察幫忙把這件事弄清楚。
Call on和call at的意思一樣，都是"拜訪""訪問"，但call on后接表示人的名詞或代詞，call at 后接表示地點或場所的詞語。試比較：
I called on the Smiths yesterday.
我昨天拜訪了史密斯一家人。
I called at the Smith's yesterday.
我昨天去了史密斯家。
I called on the doctor yesterday.
我昨天去拜訪了醫(yī)生。
I called at the doctor's yesterday.
我昨天去了醫(yī)務室。
call on還可以"號召"，后面往往接動詞不定式作賓語補主語。如：
The headmaster called on the students to work harder.
校長號召學生們更努力地學習。
Call for 有幾個不同的意思：
1．作"要求"、"需要"、"提倡"解。如：
Success calls for hard work.
成功要靠勤奮。
People are calling for the freedom of all slaves.
人們要求解放所有奴隸。
The work calls for a lot of time.
這項工作需要大量時間。
2．表示"接（某人）"、"來?。澄铮?。如：
I'll call for you at sever this evening.
今晚七點我來接你。
We call for the package at the post office.
我們到郵局去取包裹。
3．表示"喊著要人取來"，相當于ask for。如：
The man sat down and called for a glass of beer.
那人坐下來，要了一杯啤酒。
Call up是"打電話"之意，相當于ring up或telephone或phone。 如：
I'll call you up tomorrow.
我明天給你打電話。
另外，call up 還有"回想起"之意。如：
Your letter called up the days when we worked together.
你的信使我回想起我們一同工作的日子。
Your father is ill, you should call in a doctor at once.
你父親病了，應該馬上去請個大夫來。
The police have been called in to help make it clear.
已請來了警察幫忙把這件事弄清楚。
Call on和call at的意思一樣，都是"拜訪""訪問"，但call on后接表示人的名詞或代詞，call at 后接表示地點或場所的詞語。試比較：
I called on the Smiths yesterday.
我昨天拜訪了史密斯一家人。
I called at the Smith's yesterday.
我昨天去了史密斯家。
I called on the doctor yesterday.
我昨天去拜訪了醫(yī)生。
I called at the doctor's yesterday.
我昨天去了醫(yī)務室。
call on還可以"號召"，后面往往接動詞不定式作賓語補主語。如：
The headmaster called on the students to work harder.
校長號召學生們更努力地學習。
Call for 有幾個不同的意思：
1．作"要求"、"需要"、"提倡"解。如：
Success calls for hard work.
成功要靠勤奮。
People are calling for the freedom of all slaves.
人們要求解放所有奴隸。
The work calls for a lot of time.
這項工作需要大量時間。
2．表示"接（某人）"、"來?。澄铮?。如：
I'll call for you at sever this evening.
今晚七點我來接你。
We call for the package at the post office.
我們到郵局去取包裹。
3．表示"喊著要人取來"，相當于ask for。如：
The man sat down and called for a glass of beer.
那人坐下來，要了一杯啤酒。
Call up是"打電話"之意，相當于ring up或telephone或phone。 如：
I'll call you up tomorrow.
我明天給你打電話。
另外，call up 還有"回想起"之意。如：
Your letter called up the days when we worked together.
你的信使我回想起我們一同工作的日子。