单词 “period” 可以表示 “一段时间”，还可以用来表达 “阶段，时期”，学校中的 “课时”。在美式英语中，它还有 “句号” 的意思。
We'll observe the patient's weight for a period of three months.
During this period, we normally get a lot of rain.
2 “Period” 还可以表示 “（人生中或历史上的）阶段，时期”。表达这个意思时，“period” 前通常有形容词来描述这是 “怎样的” 一段时期。
I went through a difficult period when I returned to the UK.
The Elizabethan period in English literature is famous for its playwrights such as Shakespeare.
3 “Period” 用在谈论学校、上课的上下文中，可以表示 “学时，课时，一节（课）”。
I have maths in the second period on Tuesday.
There are three periods of physical education each week.
4 在美式英语中，“period” 还可以表示 “句号”，对应英式英语中的 “full stop”。
Is that a period or a comma?
I always forget to end my sentences with a period.
用法总结
1 “Period” 是名词，它的意思包括 “一段时间，时期”。表达这个意思时，常见搭配有：over/during a period（在一段时间内）；a period of time（一段时间）。We'll observe the patient's weight for a period of three months.
During this period, we normally get a lot of rain.
2 “Period” 还可以表示 “（人生中或历史上的）阶段，时期”。表达这个意思时，“period” 前通常有形容词来描述这是 “怎样的” 一段时期。
I went through a difficult period when I returned to the UK.
The Elizabethan period in English literature is famous for its playwrights such as Shakespeare.
3 “Period” 用在谈论学校、上课的上下文中，可以表示 “学时，课时，一节（课）”。
I have maths in the second period on Tuesday.
There are three periods of physical education each week.
4 在美式英语中，“period” 还可以表示 “句号”，对应英式英语中的 “full stop”。
Is that a period or a comma?
I always forget to end my sentences with a period.
