初 + Number (1–10)
The term 初五 (chūwǔ) specifically refers to the fifth day of a month in the Chinese lunar calendar. The prefix 初 is used for the first ten days of each lunar month (初一 through 初十). It is commonly seen in discussions of traditional Chinese holidays and dates.
正月初五也叫破五节。
Zhēngyuè chūwǔ yě jiào Pòwǔ Jié.
The fifth day of the first lunar month is also called the Powu Festival.
农历五月初五是端午节。
Nónglì wǔyuè chūwǔ shì Duānwǔ Jié.
The fifth day of the fifth lunar month is the Dragon Boat Festival.
我们定在初五那天出发。
Wǒmen dìng zài chūwǔ nà tiān chūfā.
We've set our departure for the fifth day.