yígòng duōshao qián?
How much in total?
今天星期几?
What day is it today?
今天 (jīntiān) means 'today', 星期 (xīngqī) means 'week', and 几 (jǐ) means 'which' or 'what number'. Together they form a question asking for the day of the week.
今天是星期几?
jīntiān shì xīngqī jǐ?
What day of the week is it today? — More formal because of the added 是 (shì).
今天几号?
jīntiān jǐ hào?
What's the date today? — Asks for the date of the month, not the day of the week.
今天星期几?
jīntiān xīngqī jǐ?
What day is it today?
今天是星期四。
jīntiān shì xīngqī sì.
Today is Thursday.
Appropriate
Avoid when
You say "今天星期几?" (jīntiān xīngqī jǐ?).
It is pronounced "jīntiān xīngqī jǐ?" with the tones: jīn (1st tone), tiān (1st tone), xīng (1st tone), qī (1st tone), jǐ (3rd tone).
Use "今天星期几?" to ask for the day of the week, and "今天几号?" to ask for the date of the month.
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