早上 (zǎo shàng) means morning, specifically the early morning hours from around 5 to 9am. 早 means early and 上 indicates the upper or start of a period. The greeting 早上好 (good morning) is standard in Mandarin-speaking regions. Related time words: 上午 (shàng wǔ, morning generally, from dawn to noon), 中午 (zhōng wǔ, noon), 下午 (xià wǔ, afternoon), 晚上 (wǎn shàng, evening). 早上 is the most specific and refers to the first hours of the day.