occur的词性是动词，在用作动词时多是用作不及物动词，是个瞬间动词，一般不用于进行时态（各类考试中常常以改错题出现）；意思是“(尤指意外地)发生；存在；出现；（想法）产生，想到”。
That plane crash occurred only minutes after take-off.
空难在起飞几分钟后就发生了。
The explosion happened〔occurred〕 during an exercise near the town.在离市镇不远的地方演习时发生了爆炸。
少数情况下，occur还可以用作系动词，其后可跟形容词作表语，表示“存在”的意思。具体用法如下：
1.occur to sb/sth发生；（观念或想法) 被想到；出现在头脑中
I hope no accident has occurred to him.
我希望他没出什么事。
Such a simple explanation never occurred to me!
我从未想到如此简单的解释。
The idea occurred to him in a dream.
这个主意是他在梦中想到的。
The same idea had occurred to Elizabeth.
伊丽莎白也想到了这个主意。
This idea never occurred to me.
（这主意）我万万没有想到。
A wonderful idea occurred to him.
他突然想到一个妙主意。
As soon as that thought occurred to him, he felt worse.
一想到那一点,他的心情就变糟。
His name did not occur to my memory.
我当时没有想起他的名字。
2.there occurred（含非be动词的存在句型）
Following the main shock there occurred a great many after-shocks.
大震以后的余震很多。
There occurred a very severe flood.
发生了一次很严重的水灾。
There occurred some misunderstanding between both sides.
双方之间发生了一些误会。
There occurred a game-changing emergency.
发生了游戏转换的紧急情况。
In March 1770, there occurred what became known as the Boston Massacre.
1770年3月在那里发生了后来闻名的波士顿惨案。
与occur一样取代be动词的表示存在的句型的词语有：happen,lie, live, stand,enter, arrive,appear,exist,follow,remain.come,occur,rise,break out,take place,come to,等
3. （想法或主意）被想到，被想起，浮现于脑海中
此时多用于否定句。如果是肯定句，一般表示突然想到。以下两个常用句型
[+ that]
It didn't occur to him that his wife was having an affair.
他没有想到自己的妻子有婚外情。
It didn't occur to me that he might have had problems.
我没有想到他可能有问题。
Didn't it occur to you that he was lying?
你当时没想到他在撒谎吗？
It occurred to me that I could have the book sent to me.
我想到可以让人把书寄给我。
It occurred to me that I had left the door unlocked.
我忽然想起来忘了锁门了。
It didn't occur to him that she would refuse his invitation.
他没有想到她会拒绝他的邀请。
It occurred to me that I had left my keys in the car.
我突然想起把车钥匙忘在了车里。
It occurred to me that I could ask my friend for help.
我想到我可以向我的朋友寻求帮助。
[+ to inf]
It didn't occur to her to ask for help.
她没想到请别人帮忙。
It did not occur to me to check my insurance policy...
我没有想到要核实我的保险单条款。
It occurred to me to visit my teacher.
我想到要去拜访我的老师。
It never occurs to them to question the doctor's decisions
他们从未想过要怀疑医生的决定。
It didn't occur to him to ask for help.他没想到请别人帮忙。
I don't suppose it occurred to you to notify the police.
我看你没想过要去通知警察。
Didn't it occur to you to close the window?难道你没有想到去关窗户吗?
Didn't it occur to you to phone them about it?关于这件事你难道就没想到给他们打个电话?
It occurred to him to tell the colonel of the problem.他想起要告诉上校那个问题。
It never occurred to me not to endeavor to do so; I was politically minded by nature.我从来没有想到过要打退堂鼓，我天生就是搞政治的。
It occurred to Tom to wonder whether Jane was quite trustworthy. Not that he thought she was in any way politically active.
汤姆突然想到简是不是值得信任，并不是说他认为简有些热衷于政治。
Mr King asked if it had ever occurred to her to make provision for her own pension
金先生问她是否曾想过要为自己的养老金预先作安排。
当然直接用occur to sb/sth
The idea occurred to him in a dream.
这个主意是他在梦中想到的。
Such a simple explanation never occurred to me!我从未想到如此简单的解释。
A wonderful idea occurred to him.他突然想到一个妙主意。
It occurred to my mind. 我当时想到了这件事。
His name did not occur to my memory.
我当时没有想起他的名字。
4. occur有时还可用作系动词,接形容词作表语,多表示“存在”。
Few metals occur free.
金属呈游离态的很少。
Silver occurs natural.
银是天然存在的。
最后看一下这个用法：
会发生第三次世界大战吗？
误：Do you think there will occur a World War III?
正：Do you think there will be a World War III?
析：“发生战争”一般不用occur，而用be。