徹夜（てつや、tetsuya）
- all-nighter

The Japanese word 徹夜, pronounced てつや (tetsuya), means to stay up all night, to stay awake all night, or to pull an all-nighter. It implies not sleeping throughout the entire night, often for work, study, or other reasons. It's a common term used to describe a situation where someone forgoes sleep for a specific purpose. It emphasizes the complete absence of sleep during the night.

⚫︎ レポートを完成させるために、徹夜した。 Translation: I stayed up all night to finish the report. ⚫︎ 試験勉強で徹夜することになった。 Translation: I ended up pulling an all-nighter to study for the exam. ⚫︎ 彼はゲームに熱中して、徹夜でプレイした。 Translation: He was so absorbed in the game that he played all night.

You use 徹夜 when you want to describe the act of staying awake through the entire night. It's typically used in situations where someone prioritizes work, study, or an activity over sleep for a specific duration of time (a single night). You can use it to explain why you are tired or the reason for your state.

徹夜 is typically written using the kanji 徹 (tetsu, meaning "thorough" or "penetrating") and 夜 (ya, meaning "night"). The reading is てつや (tetsuya) in hiragana. There is no other way to write this word as a general rule. Okurigana (the hiragana that follows the kanji) is not applicable because it is a single word.

There aren't many direct synonyms for 徹夜 that convey the same concise meaning of not sleeping the whole night. However, similar concepts can be expressed with phrases like: ⚫︎ 夜通し (yotōshi) - all night long ⚫︎ 一晩中寝ない (hitobanjū nenai) - not sleeping throughout the night ⚫︎ 夜更かし (yorukashi) - staying up late (but not necessarily all night)

The antonyms would be words related to sleeping or going to bed. ⚫︎ 睡眠 (suimin) - sleep ⚫︎ 寝る (neru) - to sleep ⚫︎ 就寝 (shūshin) - going to bed

明日のプレゼンの準備のため、昨夜は徹夜しました。 ・Translation: I pulled an all-nighter last night to prepare for tomorrow's presentation. ・Explanation: This sentence explains the reason the speaker did not sleep during the night (preparation for a presentation).

徹夜したせいで、今日は眠くて仕方ない。 ・Translation: I'm incredibly sleepy today because I stayed up all night. ・Explanation: This sentence shows the consequences of 徹夜, emphasizing the resulting sleepiness. The し is a conjugation.

The word 徹夜 is formed by combining the kanji 徹 (tetsu) meaning "thorough" or "penetrating," implying going through, or completing, and 夜 (ya) meaning "night". The combination suggests the act of "penetrating" or "going through" the entire night without sleep.