明るさ
akarusa
The English phrase "brightness" is translated into Japanese as 明るさ (akarusa).
明るさ is the noun used to express the quality or level of brightness. If you wish to describe something as being blindingly bright, you can use 眩しい. In formal contexts, such as physics or engineering, the term 光度 is used to indicate luminous intensity or brightness.
Meaning: the quality of being bright (noun)
What does it mean word for word?
The word 明るさ is formed by taking the adjective stem of 明るい (bright) and adding the suffix -さ, which converts adjectives into nouns representing a specific degree or quality.
Which one should you use?
明るさ refers to the abstract quality or level of brightness itself, whereas the adjective 明るい is used to describe a specific object that possesses that quality.
How does it change in a sentence?
While 明るさ is the noun meaning 'brightness', the adjective 明るい is used when you want to describe a specific object as being bright.
How do you pronounce it?
akarusa
Did you know?
- The kanji 明 is composed of two parts: the 'sun' 日 and the 'moon' 月, combining the two brightest objects in the sky to mean 'light'.
- In Japanese, a person who is 'bright' in a certain subject is not described with 明るい, but rather 得意 or 詳しい.
- While 明るさ refers to the physical brightness of light, it is also used metaphorically to describe a person's 'brightness' in terms of their cheerful or sunny personality.
Examples in context
- 彼女の部屋の明るさは心地よい。The brightness in her room is pleasant.
- その輝度計は光源の明るさを正確に測定する。That photometer accurately measures the brightness of the light source.
- この部屋は明るすぎて目が痛いよ。This room is too bright, it hurts my eyes.
- あの星の光がとても明るいね。The light from that star is very bright.
- この照明は明るさが足りない。Kono shoumei wa akarusa ga tarinai.This lighting lacks brightness.
- 画面の明るさを調整してください。Gamen no akarusa o chousei shite kudasai.Please adjust the brightness of the screen.
- 部屋の明るさが変わりました。Heya no akarusa ga kawarimashita.The brightness of the room has changed.
Example conversation
A son and daughter are sitting in the living room adjusting the lights.
- 陽太 Yota陽葵、この部屋の明るさはどうかな？Himari, kono heya no akarusa wa dou kana?Himari, how is the brightness in this room?
- 陽葵 Himariもう少し明るいほうがいいと思う。Mou sukoshi akarui hou ga ii to omou.I think it should be a bit brighter.
- 陽太 Yotaじゃあ、照明をもう少し強くするね。Jaa, shoumei o mou sukoshi tsuyoku suru ne.Then, I'll make the lighting a bit stronger.
- 陽葵 Himariありがとう、陽太くん。Arigatou, Youta-kun.Thank you, Youta.
Sources
- Wiktionary, “brightness” translations, CC BY-SA 4.0, dump of 2026-09-26.
