Example sentences
shàng上wǔ午yǒu有huì会ma吗？
Is there a meeting in the morning?
wǒ我shàng上wǔ午qù去。
I'll go in the morning.
About this word
上 means "above, upper" and 午 means "noon". 上午 is the part of the day above noon, meaning before it. The system is tidy in threes: 上午 (morning), 中午 (noon, literally "middle noon"), 下午 (afternoon, the part below noon). 午 started as one of the twelve earthly branches and got tied to the middle of the day, and it also shows up in 午饭 (lunch) and 午夜 (midnight). For the hours right after waking, Chinese more often says 早上.
The story behind the character
上
A line with a short mark above it, meaning "on top of." This kind of character isn't drawn, it's indicated. Xu Shen wrote 上, 高也: "up, high." Fun fact: it used to be two lines, and the vertical stroke was added later to stop it being confused with the number 二.
午
午 is a pestle: thick at both ends, thin in the middle, the stick for pounding grain. That is how most scholars read it. Xu Shen glossed it differently, 午, 啎也, to go against, which follows the sound more than the picture. 午 got borrowed for the seventh earthly branch, the one covering eleven to one, so midday is 午. The pestle had to be reissued as 杵.