num.八十，八十几，八十年代
n.八十几，八十年代

原形：eighty复数：eighties

Mary is eighty years old.
玛丽八十岁了。
This room has eighty guests.
这间房子里有80位客人。
She scored eighty points in the math test.
她在数学考试中得了80分。
There are eighty students in our class.
我们班有80名学生。
The book costs eighty dollars.
这本书的价格是80美元。
He worked eighty hours a week during the summer job.
他在暑期工作时每周工作80小时。
She's eighty years old, but still active.
她八十岁了，但仍然很活跃。
The marathon distance is eighty kilometers.
马拉松的距离是80公里。
They finished the project in eighty days.
他们用了80天完成了项目。
The temperature dropped to eighty below zero.
气温下降到了零下80度。
There are eighty countries participating in the Olympics.
有80个国家参加奥运会。
Eighty percent of the students passed the exam. (80%的学生通过了考试。
请注意，"eighty"在不同的语境中可能与具体的单位（如分数、温度、货币等）相关联，上述例句都考虑了通用的用法。