Quick Reference

Meaning & Definition

火曜日 (kayoubi) literally means “fire day” — the 火 (fire) in its name traces back to Mars, the red planet known in Japanese as 火星 (kasei, “fire star”). Every time a Japanese speaker says 火曜日, they are invoking a 2,000-year-old system that maps the seven days of the week onto celestial bodies and natural elements.

火曜日 is the standard Japanese word for Tuesday, used in all registers from casual texting to formal business writing. It follows 月曜日 (Monday) and precedes 水曜日 (Wednesday) in the week. The short form 火曜 (kayou) is common in speech and informal writing. Like all Japanese weekday names, 火曜日 ends in 曜日 (youbi), the general word for “day of the week,” so the literal breakdown is 火 (fire/Mars) + 曜日 (day of the week). It can be used alone as a time reference (“on Tuesday”) or combined with particles to express schedules, deadlines, and appointments.

How to Use It

The key particle to learn with 火曜日 is に (ni) to express “on Tuesday”: 火曜日に会議があります (There is a meeting on Tuesday). Do not confuse this with 火曜日の, which acts as a modifier — 火曜日の締め切り means “Tuesday’s deadline” (a deadline that belongs to Tuesday). The short form 火曜 works in casual contexts: 火曜に来て (Come on Tuesday). When writing dates, Japanese typically orders year → month → day → day-of-week, so you might see 6月24日（火）with 火 in parentheses as the abbreviation for 火曜日.

Kanji Breakdown

火 (hi / ka) means “fire” and also represents the planet Mars (火星, kasei — literally “fire star”). 曜 (you) means a day of the week in the seven-day cycle; its radical 日 (sun/day) reflects the astronomical origin of the system. 日 at the end simply means “day.” Together, 火曜日 encodes Mars → fire → Tuesday in a single three-character compound that has been in use in Japan since the Heian period (794–1185).

Example Sentences

Cultural Context

Japan’s seven-day week (七曜, shichiyou) assigns each day to one of seven celestial bodies: Sunday (日, Sun), Monday (月, Moon), Tuesday (火, Mars), Wednesday (水, Mercury), Thursday (木, Jupiter), Friday (金, Venus), and Saturday (土, Saturn). This system entered Japan via China and India around the 9th century, ultimately derived from Hellenistic astrology. 火曜日’s association with Mars — the red, fiery planet — is what gave it the character 火. Japanese schoolchildren learn this planetary mapping early, making 火曜日 one of the first weekday kanji they recognize.

In modern Japanese consumer culture, Tuesday has a quiet but real identity as a discount day. Many cinemas designate Tuesday as “Men’s Day” (メンズデー) with reduced ticket prices — a counterpart to the better-known Ladies’ Day on Wednesday. Some supermarkets and online retailers run 火曜セール (Tuesday sales). This makes 火曜日 a word that appears frequently in flyers, app notifications, and LINE messages, giving learners plenty of real-world exposure beyond simple calendar use.

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