Word
Kana: にちや Romaji: nichiya Level: N1

日夜

Meaning in English

day and night, always

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Word context

What it means

日夜 means day and night; it is used to describe constant, uninterrupted activity or presence across both day and night, often in formal or literary contexts.

Main meanings

  • day and night; around the clock, indicating constant operation or attention.
  • continuous effort, vigilance, or activity that spans all hours of the day and night.
  • figurative sense of perpetual or unceasing dedication or scrutiny.

How to use it

Used in formal writing, legal language, historical or literary narration, and in everyday speech in compound forms such as 日夜を問わず; when used alone, it often functions as a noun or adverbial phrase describing ongoing, round-the-clock activity.

Variants and close terms

  • 昼夜 (ちゅうや, chuya) — day and night, commonly used as a synonym in similar contexts
  • 一日中 (いちにちじゅう, ichinichijū) — all day long
  • 絶えず (たえず, taezu) — constantly
  • 夜通し (よどおし, yodōshi) — through the night

Composition

  • 日: day; sun
  • 夜: night
  • Combined meaning conveys the full cycle of time and the sense of constancy across all hours

Etymology

日夜 combines the on-reading 日 (nichi) and 夜 (ya), forming a Sino-Japanese compound whose standard reading is nichiya and that has been used in formal language to express continuous time across day and night.

Origin

The concept appears in classical Japanese writings influenced by Chinese literary traditions, with the sense of a continuous cycle day and night; its prominence grows in formal, bureaucratic, and literary registers from the medieval to early modern periods.

Word class

expression (日夜) — noun/adverbial phrase

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