Compound of *alle* (all, every) + *Tag* (day), literally "every day." The word emerged in Early Modern High German and became standard in the 18th century. Its antonym *Feiertag* (holiday, feast day) highlights the contrast between the sacred and the mundane encoded in German compound nouns.

Germans frequently invoke *Alltag* in discussions of work-life balance (*Alltagsstress*, everyday stress) and mental health. The compound *alltagstauglich* ("fit for everyday use / practical") appears in product descriptions and political speech. Beware of the false friend trap: English "all day" sounds similar but means something different — *Alltag* is about routine, not duration.