星期一 (xīng qī yī) means “Monday”

More examples

我星期一有中文课。wǒ xīng qī yì yǒu zhōng wén kè

I have Chinese class on Monday.

The first numbered place in the repeating seven-day cycle.

周一zhōu yī: A short, commonly spoken name for Monday.
礼拜一lǐ bài yī: An everyday conversational name for Monday.

表示一周的第一日，通常指周一，用于表述日期或约定时间。biǎo shì yì zhōu de dì yí rì tōng cháng zhǐ zhōu yī yòng yú biǎo shù rì qī huò yuē dìng shí jiān

星期一 (xīngqīyī, "Monday") combines 星期 (xīngqī, "week") with 一 (yī, "one") to name day one of the week.

On a timetable, this word identifies a recurring weekly slot rather than a date that changes from year to year.