隔日 (gé rì) literally combines 隔 (gé), meaning 'to separate' or 'to skip', and 日 (rì), meaning 'day'. Together, it expresses the idea of skipping one day between occurrences — that is, happening every other day. It functions primarily as an adverb indicating frequency, similar to 'bi-daily' in English (though not to be confused with 'twice daily').

This term is commonly used in schedules, medical instructions, exercise routines, and habit tracking. It implies regular alternation: if an activity happens on Monday, the next occurrence is Wednesday, then Friday, and so on. Unlike 每两天 (měi liǎng tiān), which can be ambiguous, 隔日 unambiguously means 'with one day in between' and is widely preferred in formal and spoken contexts for clarity.