protection of a person, building, organization, or country against threats such as crime or attacks by foreign countries

The station was closed for two hours because of a security alert. 由于有安全警报，车站关闭了两小时。

30 demonstrators were killed in clashes with the security forces over the weekend. 周末，30名示威者在与保安部队的冲突中丧生。

The tighter security measures/precautions include video cameras throughout the city centre. 加强安全保障措施包括在市中心安装摄像头。

The students were deported because they posed a threat to national security. 这些学生因对国家安全构成威胁而被驱逐出境。

The banks must tighten security against fraud. 银行必须加强安全措施，防止诈骗。

The most dangerous criminals are held in maximum-security prisons (= prisons that are as difficult as possible to escape from). 最为危险的罪犯被关押在戒备最森严的监狱里。

the group of people responsible for protecting a building

You'll need to notify security if you want to work late in the office. 如果想在办公室里工作到很晚，你需要通知保安人员。

the fact that something is not likely to fail or be lost

If it's a choice between higher pay and job security, I'd prefer to keep my job. 如果在更高的薪酬和安稳的工作两者之间进行选择，我宁愿保住工作。

I'm on a temporary contract and have little financial security (= cannot be sure of having enough money to live on). 我签的是临时合同，没什么经济保障。

property or goods that you promise to give to someone if you cannot pay what you owe them

She used her shares in the company as security against a $23 million bank loan. 她用自己在公司的股票作抵押向银行借了2300万美元。

The hotel held onto our suitcases as security while we went to the bank to get money to pay the bill. 宾馆扣下我们的行李作为抵押，我们则去银行取钱来付账。

investment in a company or in government debt that can be traded on the financial markets and produces an income for the investor

He pleaded guilty to three counts of securities fraud.

The deals represented 74 percent of all such securities issued in that year.

Prices in these particular securities markets can be volatile.

As a result, he was prevented from conducting securities transactions for a period.

This is something that securities regulators want changed.

the feeling of being confident in one's family and relationships

Most children need the security of a stable family life. 大多数孩子需要稳定的家庭生活带来的安全感。