这三个词都表示“发生”，但是有一定的区别：
1.happen v. 发生
普通用词，多用于偶然事件。
The accident happened at 5 o'clock.
事故发生在5点钟。
What happened to you (the radio)? 你(收音机)怎么样了?
What happened then?
后来又发生了什么事？
She happened to be out when he called.他打电话时, 她恰巧不在家。
表示某一事的发生是因为另一事的结果，通常用 happen。如：
What happened when you told her the news? 你告诉她这个消息时，她有何反应?
2.occur v. [正式]发生
可用于偶然事件或计划之事，可与 happen 换用。
The earthquake occurred/happened at dawn.
地震发生在黎明时分。
The murder occurred at about 3:00pm. 凶杀案大约发生在下午三点。
The accident happened /occurred at about 10. 事故大约发生在 10 点钟。
A serious traffic accident occurred/happened yesterday.
昨天发生了一起严重的交通事故。
3.take place phr. v. 发生，举行
主要用于事先计划好规划好的的事情。
The meeting will take place on Sunday. 会议星期日举行。
Great changes have taken place in China.
中国发生了翻天覆地的变化。
Great changes have taken place in the past three decades.过去三十年发生了很大变化。
The parade will take place on Sunday, rain or shine.
庆祝游行定于星期日举行，风雨无阻。
The wedding will take place next Saturday. 婚礼将在下周六举行。
The Olympics take place every four years.奥运会每四年举行一次。
三者表示“发生”都是不及物动词，因此既不能带宾语，也不能用于被动语态。如：
How did the accident happen [occur]? 事故是怎样发生的?
Elections take place every four years. 每 4 年举行一次选举。
另外，break out爆发，发生（战争，战斗；意想不到的事情）
He was 29 when war broke out.
战争爆发时他才29岁。
The authorities have urged people to stock up on fuel in case hostilities break out.
当局已敦促人们储存燃料，以防战事爆发。
Dark clouds were gathering in the skies over Europe. War was soon to break out.
欧洲上空乌云密布，战争即将爆发。
Armed conflict may break out at any moment.
武装冲突有一触即发之势。
Fighting broke out in three districts of the city last night.
昨夜这座城市有三个区发生了战斗。
Where were you living when war broke out?
战争爆发时你住在哪儿？
We can fix the ship's exact position at the time the fire broke out.
我们可以确定发生火灾时那艘船的确切位置。
They had escaped to America shortly before war broke out in 1939.
1939年战争爆发前不久他们逃到了美国。
Rioting broke out in the capital.
首都爆发了骚乱事件。
Violence has broken out in the capital, a stark reminder that the religious tensions are refusing to go away.
首都爆发了暴力事件，这给了人们一个严酷的提醒——宗教紧张局势还在持续。
A row has broken out over education.
在教育问题上出现了严重分歧。
Most of the occupants had left before the fire broke out
大部分住户在火灾发生前就已经离开。
Fires broke out at three railway stations, halting service on two commuter lines for several hours
三个火车站发生了火灾，两条通勤线路的服务被迫中断数小时。
A few minutes after take-off, the pilot radioed that a fire had broken out.
起飞几分钟后，飞行员用无线电报告说飞机内突然起火。
Fire broke out during the night.
夜间突然发生了火灾。
The plague has broken out.
突然发生了鼠疫。
A fight broke out between rival groups of fans.
比赛双方球迷打了起来。
Fighting had broken out between rival groups of fans.
双方球迷发生了打斗。
Clashes broke out between police and demonstrators.
警方与示威者发生了冲突。
Another time of great excitement for us boys was when war broke out
对我们男孩子来说另一个极度刺激的时刻是战争爆发。
Communal violence broke out in different parts of the country.
在该国不同的地区发生了群体暴力事件。
Her family was given safe conduct to Britain when civil war broke out.
内战爆发时，她全家获得了前往英国的安全通行许可。
The fighting broke out about two hours after sundown.
日落后大约两小时战斗打响了。
Gunfire broke out early this morning around the seat of government in Lagos.
今天凌晨在拉各斯的政府大楼周围发生了枪战。
The minister warned that if war broke out, it would be catastrophic for the whole world.
这位部长警告说，万一爆发战争，那对全世界都将是场灾难。
He had no sooner got his wings than the Korean conflict broke out.
他刚获得飞行资格，朝鲜战争就爆发了。
Shooting broke out after the guards surrounded a villa in the city.
卫兵包围了该市的一所别墅后便发生了枪战。
Fighting had broken out and all was chaos and confusion.
战斗爆发了，一切都陷入了混乱不堪的状态。
Do you think there will be a World War III? 会发生第三次世界大战吗？
析：“发生战争”一般不用occur，而用break out或be。
arise 刚开始出现（正式用语）
一般用于表示不在预期内出现的问题、困境或者机会等。
注意：arise是比较正式的表达，口语中一般使用come up.
例句：
A crisis arose as soon as he left the company.
他刚从公司离开，危机就发生了。
A crisis has arisen in the Foreign Office.
外交部出现了危机。
Difficulties arose in his work.
他工作中出现了困难。
A storm arose during the night.
夜间暴风雨大作。
Whatever troubles arise, we'll have peace of mind amidst seeming chaos.
无论出现什么样的麻烦，我们都会在貌似混乱的情形中保持平和的心态。
The problem first arose in 2003.
这个问题首次出现在2003年。
A number of problems have arisen.
已经出现了一些问题。
A vacancy has arisen which I intend to fill.
有一个职位空了出来，我想要补上。
When children enter the equation, further tensions may arise within a marriage.
有了孩子以后，婚姻中可能出现新的矛盾。
Disagreement arose about exactly how to plan the show.
在如何拟定具体演出计划的问题上出现了分歧。
In the unlikely event of a problem arising, please contact the hotel manager.
万一出现问题，请找旅馆经理。
In a good marriage, both husband and wife work hard to solve any problems that arise
美满的婚姻中，夫妻双方会共同努力去解决出现的任何问题。
Ring regularly to check that no unforeseen problems have arisen.
定期打个电话，确认一下有没有意外情况。
Any unexpected circumstance that arises may catalyze a sudden escalation of violence.
任何突如其来的情况都可能造成暴力骤然升级。
Another flight would be arranged on Saturday if sufficient demand arose
如果需求量足够大，周六将再安排一趟航班。
Plant out the spring cabbage whenever opportunities arise.
一有机会就把春季卷心菜移种到地里。
The birds also attack crops when the opportunity arises.
一有机会鸟儿们也会破坏庄稼。