Days Of The Week In Japanese [and Their Awesome Celestial Meanings!]

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So, you’ve come here to learn the days of the week in Japanese!

Now, I could simply list off each day of the week and its Japanese counterpart for you to then learn off by heart…

However, I just cannot deny you the seriously interesting etymology behind the terms! Did you know the days in Japanese are all named after different planets and other celestial bodies? 🌞🪐🌙🌌

Additionally, in language learning, it’s really helpful to memorise new words through associations.

Let’s start with a quick reference guide to the days of the week in Japanese:


You probably noticed that each day ends in the term youbi (曜日 / ようび), which means ‘day of the week’.

Similarly to English days of the week, in Japanese there is a specific prefix (with varying meanings) attached to the beginning of the word ‘day’ to make up each day of the week.

We’ll go into more detail on the meaning and origins of each name below!

Download a FREE printable workbook to learn the Japanese scripts hiragana and katakana here.

Important points to note

There are a few facts to know which explain the origins of the Japanese names for each day of the week.

  • The seven days of the week relate to seven celestial bodies in our solar system – the moon, the sun, Mars, Mercury, Jupiter, Venus and Saturn! The same is true in other languages across the world, such as French and other Romance languages.
  • The days of the week also contain kanji characters from the Chinese elemental system, known as wuxing. The five natural elements are fire, water, wood, metal and earth and it is believed that everything in the universe comes from these elements.
  • As we will be discussing various kanji characters, we’ll talk about onyomi and kunyomi pronunciations. Onyomi (音読み / おんよみ) literally translates as ‘sound reading’ and derives from Chinese pronunciation. On the other hand, kunyomi (訓読み / くんよみ) translates as ‘meaning reading’ and relates to readings originating from native Japanese. Depending on whether the kanji or word is used as a standalone term, or in a compound, the pronunciation will vary.
A group of children holding up planets on a blue background to demonstrate the celestial origins of the days of the week in Japanese.

Days of the week in Japanese




If you have read our post about the moon in Japanese, you may already know that getsuyoubi (月曜日 / げつようび) is, of course, ’Monday’!

Although the Japanese word for ‘moon’ is tsuki, the kanji character for moon,月, is pronounced as getsu in this kanji compound. 

This is the same reason we say ‘Monday’ in English, as it was originally ‘Moon’s day’.

A beautiful full moon illuminating a majestic Japanese castle. The Japanese day of the week getsuyoubi/Monday means 'moon day', the same as in English.




Kayoubi (火曜日 / かようび) is Japanese for ‘Tuesday’. The kanji character 火 meaning ‘fire’, is one of the five natural elements mentioned previously.

So, you may be wondering “Fire day? How exactly does kayoubi relate to a celestial body?” The answer is that it actually stems from the word kasei (星 / かせい), which is the Japanese term for the planet ‘Mars’! 

The second kanji character in 火星 (Mars) means ‘star’. It’s important to note that while the word for ‘star’ in Japanese is hoshi, in this particular word compound we use the onyomi pronunciation, sei.

Mars is often referred to as the red planet, scattered with many volcanoes, so kasei is a pretty spot on name!




Suiyoubi (水曜日 / すいようび) is the Japanese word for the hump day of the week, ‘Wednesday’!

The kanji 水 means ‘water’, another one of the five elements of ancient Chinese cosmology. Suisei (星 / すいせい) is the Japanese term for the planet ‘Mercury’.

That being said, we use the kunyomi reading of mizu when talking about water, especially drinking water. 




Mokuyoubi (木曜日 / もくようび) is ‘Thursday’ in Japanese. Take a look at the first kanji and make a guess at what it is trying to depict!… If you guessed ‘tree’, you would be correct!

It refers to the natural element of ‘wood’. Although an actual ‘tree’ in Japanese would be pronounced as ki, in certain kanji combinations such as this one, it is pronounced as moku

In line with the previous examples, you would be right in thinking that mokusei (製 / もくせい) is another celestial body! Mokusei refers to the planet ‘Jupiter’, the largest planet in our solar system. 




Kinyoubi (金曜日 / きんようび) is the Japanese term for ‘Friday’. Perhaps you recognise the kanji 金 from our post about money in Japanese! It can be translated as ‘gold’ or ‘money’. Therefore, a great way to remember the word for Friday is to think of kinyoubi as pay day!

Kinsei (星 / きんせい) is Japanese for the planet ‘Venus’ and kin alludes to the natural element of ‘metal’.




Doyoubi (土曜日 / どようび) means ‘Saturday’ and 土 refers to ‘earth’ or ‘ground’, which is of course the final natural element on our list. Dosei (星 / どせい) is the planet of ‘Saturn’!

We can also clearly see that the English word for ‘Saturday’ is also closely derived from the ringed planet. It used to be referred to as ‘Saturn’s day’.




Nichiyoubi (日曜日 / にちようび) is Japanese for ‘Sunday’. As mentioned in our previous post about the sun in Japanese, the etymology of nichiyoubi  is rather straightforward as it is made up of the words ‘sun’ and ‘day’, paralleling English! 

Remember that when talking about the actual sun itself, we generally use the kunyomi reading hi (ひ).

A Japanese calendar featuring a serene snowy scene and days of the week in Japanese kanji characters.
A Japanese calendar, showing the days of the week in Japanese. A couple of interesting things to note: firstly, the week starts on Sunday (日曜日) in Japanese calendars. Secondly, see how each day is represented by the first kanji in its name (i.e. 月 is used as shorthand for月曜日). Image source: Ph0kin, CC BY-SA 4.0, via Wikimedia Commons

Now you know how to say the Japanese days of the week!

We hope you agree, learning the meaning behind the names of the days of the week in Japanese is fascinating… and also makes them easier to remember!

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Hannah Stafford

Hannah is a half Irish/half Japanese girl living in Ireland. Her love for Japan and the Japanese language led her to studying languages and translation in university where she specialised in Japanese. She spent a year studying abroad at Rikkyo University in Tokyo. In her free time, Hannah enjoys using her sewing machine to upcycle clothes and create new pieces!

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