Number + 月份
月份 (yuèfèn) means "month" and is used when referring to months in a general or categorical sense, such as discussing which month something occurs in. It differs from 月 alone, which is used more directly with numbers (e.g., 三月 for March). 月份 often appears in contexts like surveys, reports, and schedules.
你知道哪个月份的机票最便宜吗?
Nǐ zhīdào nǎge yuèfèn de jīpiào zuì piányi ma?
Do you know which month has the cheapest flights?
请在表格上填写出生月份。
Qǐng zài biǎogé shàng tiánxiě chūshēng yuèfèn.
Please fill in your birth month on the form.
北京最热的月份是七月和八月。
Běijīng zuì rè de yuèfèn shì qīyuè hé bāyuè.
The hottest months in Beijing are July and August.