There are two ways of expressing a notice period, as follows:
　　“通知期限”的表达方式有以下两种：
　　1.Under Clause 4.2 one month’s notice is required in order to terminate the agreement.
　　根据条款4.2的规定，终止协议前须要有一个月的通知期限。
　　2.Under Clause 4.2 a one-month notice period is required in order to terminate the agreement.
　　根据条款4.2的规定，终止协议前须要有一个月的通知期限。
　　Anything else, or a mixture of these two constructions, is wrong. Note than in the first example above “notice” is an uncountable noun so it cannot take “a/an”. In the second example, “notice period” is countable, so we must say “a notice period”. “One-month” is a compound adjective, so a hyphen (-) is required.
　　除了以上两种表达，其余的表达或者混合这两种的表达都是错误的。第一种表达中，“notice”是不可数名词，所以前面不需要加“a/an”。而第二种表达中，“notice period”是可数的，所以一定要用“a notice period”来表示。“one-month”在这里是复合形容词，当中需要加连字符。
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　　More example:
　　更多例子：
　　Three months’ notice of an intention to terminate an employment contract is required after an employee has been employed for three years.
　　员工入职三年后，其终止用工合同的通知期限自动升级为三个月。
　　A three-month notice period of an intention to terminate an employment contract is required after an employee has been employed for three years.
　　员工入职三年后，其终止用工合同的通知期限自动升级为三个月。
　　Remember that in this sense of the word “notice” is uncountable, so you cannot give somebody a notice. You can only give somebody notice. But of course you can give somebody a week’s notice because “a” refers to “week” (and means “one”). In the same way you give somebody two weeks’ notice etc.
　　记住，当句子中的“notice”是不可数名词时，就不能用给某人一个期限（give somebody a notice），只能表达为给某人期限（give somebody notice）。但是，你可以给某人一周的期限（give somebody a week’s notice），因为这里的“a”修饰的是“week”，同样“a”也可以换成“two”，比如给某人两周的期限（give somebody two week’s notice）。