should 是情态动词,后接动词原形。should译为应该；大概是，有可能；将会，shall，can, may,must等都是情态动词，它们不能独立作谓语，只能和动词原形一起构成谓语。举例：People should diversify their investments.人们应分散投资在几家公司。should there be a flood, what should we do? 万一发生水灾我们怎么办？
Should的用法
1.should后直接跟动词原形，没有人称和数的变化, 如：
You should go home at once.He should eat more vegetables.I should finish my homework before nine.should的否定形式是在should后面加not, 可以缩写为shouldn’t, 意为“不应当; 不应该”。如:You should not / shouldn’t insult her. 你不应该羞辱她。
2.should作为情态动词最基本的意思是“应该”，既可指建议或劝告某人“应该”做某事，也可指有责任或义务“应该”做某事，如：You should tell your mother. 你应该告诉你的妈妈。
3.should可以与say, think, imagine等动词连用，使语气变得委婉，如：I should say he is an English teacher. 我想他是一位英语老师。I should think it is a good song. 我想那是一首好曲子。
`But what should I sing?' she interrupted him, keenly.
“可是我该唱什么呢？”她打断他的话，满心期待地问。
Dolly is myopic and should see an optician.
多莉是近视眼，应该看看眼科医生。
He should get an uncontested lead.
毫无疑问，他会获得领先。
4You should have seen him, it was hysterical!
你真该看看他的样子，那真是乐死人了！
5The boxes should be constructed from rough-sawn timber.
这些箱子应该用粗锯木料来做。
