a.m.

英 [ˌeɪ ˈem]

美 [ˌeɪ ˈem]

abbr. 午夜至正午，上午，午前(源自拉丁语ante meridiem)

Collins.2

牛津词典

abbr.

午夜至正午，上午，午前（源自拉丁语ante meridiem）
between midnight and midday (from Latin ante meridiem )
1. It starts at 10 a.m.
  上午10点开始。

上午；午前
a.m. is used after a number to show that you are referring to a particular time between midnight and noon.
1. The program starts at 9 a.m.
  节目上午9点开始。

adj

We have flight at 8:30 a.m. and 4:00 p.m.
我们有上午8点30分和下午4点的班机。
This hands-on management approach often stretches his workday from 6 a.m. to 11 p.m.
这种亲历亲为的管理方法经常让他从早上6点一直工作到晚上11点。
But it's quite another story for those of us who have to be at work by8 a.m.
但那对我们这些得在八点前上班的人来说就完全是另外一回事了。
Compute their utilization rate for the peak hour, Mondays from 8:00-9:00 a.m.
计算他们在尖峰时段；星期一早上8：00-9：00的利用率。
The program starts at 9 a.m.
节目上午9点开始。
He arose at 6:30 a.m. as usual.
同往常一样，他在早上6:30起了床。
The train will depart at 7:30 a.m.
早七点半发车。
Can I get a seat for today's 7:00 a.m. train?
我可以买到今天上午7点的火车座位吗？
I spotted a clock: 3:00 a.m.
我看了一眼钟：凌晨2点。
I pored over the books with great enthusiasm, often crunching the numbers until 1:00 a.m.
我兴致勃勃地研究这些账簿，经常计算到凌晨1点。