曜 (よう / yō) = “day of the week” (borrowed from Chinese)
日 (び / bi) = “day”
So, 曜日 = day of the week
Each day is named after elements inspired by the Five Elements theory (五行) and Seven Luminaries (七曜): Sun, Moon, and the 5 classical planets.
1. Historical Origins
The 7-day week came from Babylonian astronomy, passed through India, and was adopted in China by the 4th–5th century via Buddhism and astrology.
The Chinese named the days after the Sun, Moon, Mars, Mercury, Jupiter, Venus, and Saturn — linked with yin-yang and wu xing (Five Elements).
2. The 7 Days of the Week in Japanese
| Japanese | Kanji | Meaning | Origin | Tiếng việt |
|---|---|---|---|---|
| 月曜日 (げつようび) | 月 = Moon | Monday | Moon day | Thứ hai |
| 火曜日 (かようび) | 火 = Fire (Mars) | Tuesday | Mars day | Thứ ba |
| 水曜日 (すいようび) | 水 = Water (Mercury) | Wednesday | Mercury day | Thứ tư |
| 木曜日 (もくようび) | 木 = Wood (Jupiter) | Thursday | Jupiter day | Thứ năm |
| 金曜日 (きんようび) | 金 = Metal (Venus) | Friday | Venus day | Thứ sáu |
| 土曜日 (どようび) | 土 = Earth (Saturn) | Saturday | Saturn day | Thứ bảy |
| 日曜日 (にちようび) | 日 = Sun | Sunday | Sun day | Chủ nhật |
🌕 月曜日（げつようび / Getsuyoubi – Monday）
- 月 (げつ / getsu) = Moon
- 曜日 (ようび / youbi) = Day of the week
➡️ 月曜日 = “Moon Day” = Monday
1. Meaning & Origin
2. Related Words / Variants
- 月 (つき) – Moon
- 月曜 (げつよう) – Shortened form
- 月曜日から始める – Start from Monday
I believe my Monday not is moon day, that is task day 😂.
🔥 火曜日（かようび / Kayoubi – Tuesday）
1. Meaning & Origin
- 火 (か / ka) = Fire (planet Mars)
➡️ 火曜日 = “Fire Day” = Tuesday
2. Related Words / Variants
- 火 (ひ) – Fire
- 火災 (かさい) – Fire (disaster)
- 火曜ドラマ – Tuesday drama
💧 水曜日（すいようび / Suiyoubi – Wednesday）
1. Meaning & Origin
- 水 (すい / sui) = Water (planet Mercury)
➡️ 水曜日 = “Water Day” = Wednesday
2. Related Words / Variants
- 水 (みず) – Water
- 水泳 (すいえい) – Swimming
- 水曜スペシャル – Wednesday Special
🌳 木曜日（もくようび / Mokuyoubi – Thursday）
1. Meaning & Origin
- 木 (もく / moku) = Wood (planet Jupiter)
➡️ 木曜日 = “Wood Day” = Thursday
2. Related Words / Variants
- 木 (き) – Tree
- 木陰 (こかげ) – Shade of a tree
- 木曜ミステリー – Thursday Mystery Show
💰 金曜日（きんようび / Kinyoubi – Friday）
1. Meaning & Origin
- 金 (きん / kin) = Gold/Metal (planet Venus)
➡️ 金曜日 = “Gold Day” = Friday
2. Related Words / Variants
- お金 (おかね) – Money
- 金色 (きんいろ) – Golden color
- 花金（はなきん） – “Thank-God-It’s-Friday” (casual)
🌍 土曜日（どようび / Doyoubi – Saturday）
1. Meaning & Origin
- 土 (ど / do) = Earth/Soil (planet Saturn)
➡️ 土曜日 = “Earth Day” = Saturday
2. Related Words / Variants
- 土 (つち) – Soil
- 土地 (とち) – Land
- 土曜アニメ – Saturday Anime
日曜日（にちようび / Nichiyoubi – Sunday）
1. Meaning & Origin
- 日 (にち / nichi) = Sun
➡️ 日曜日 = “Sun Day” = Sunday
2. Related Words / Variants
- 太陽 (たいよう) – The sun
- 日差し (ひざし) – Sunlight
3. Related Words / Variants
- 今日（きょう・kyou）= Today
- 明日（あした・ashita）= Tomorrow
- 昨日（きのう・kinou）= Yesterday
- 毎日（まいにち・mainichi）= Every day
- 週末（しゅうまつ・shuumatsu）= Weekend
- …
4. Example Easy Conversation (N5 Level)
A: すみません、今日は何曜日ですか？
Sumimasen, kyou wa nan youbi desu ka?
Excuse me, what day of the week is it today?
B: 木曜日です。
Mokuyoubi desu.
It’s Thursday.
A: ありがとうございます！
Arigatou gozaimasu!
Thank you!
Hey, today, may be learning overheat, let’s take a rest.
