每星期 means 'every week' and functions as a time-frequency adverb in Chinese. It is composed of three characters: 每 (měi), meaning 'each' or 'every'; 星 (xīng), short for 星期 (xīngqī), meaning 'week'; and 期 (qī), which here reinforces the sense of 'period' or 'cycle'. Together, they form a fixed phrase indicating regular recurrence once per seven-day cycle. It typically appears before verbs or at the beginning or end of a sentence to specify how often an action occurs.

This phrase is neutral in register and widely used in both spoken and written Mandarin — in schedules, routines, announcements, and personal plans. While 每星期 is common in Mainland China, speakers in Taiwan often prefer 每週 (měi zhōu), using the character 週 instead of 星期. Both are grammatically interchangeable, though 每星期 is more frequent in everyday mainland usage, especially in informal contexts like conversations or text messages.