昨 — Yesterday, Previous, Last

Meaning

昨 means "yesterday" and, more broadly, "the previous time period." Attach it to any time noun — day, year, night, morning, season — and it shifts that word one step into the past. 昨日 is yesterday, 昨年 is last year, 昨夜 is last night.

Structurally, 昨 combines two components: 日 (にち／ひ), meaning "sun" or "day," on the left, and 乍 (さ) on the right — a character that originally conveyed the idea of something sudden or momentary. Picture a day that crossed the sky and ended. That image of a sun already set fixed the meaning: the day immediately before today, and by extension any recently passed time period.

昨 has 9 strokes and enters the Japanese school curriculum in Grade 4, around age 10. Its radical is 日. In practice, the character never stands alone — it works as a prefix, snapping onto nouns like 日, 年, and 夜 to form compound words.

昨日 and 昨年 appear constantly in newspaper headlines, business emails, and everyday speech. Learning this single character unlocks a whole family of high-frequency time expressions.

Readings

On'yomi (音読み) — Chinese-derived readings

昨 has one on'yomi: サク (saku). It's consistent across all compounds — with one exception. Before 今 (こん), the reading contracts to さっ, producing 昨今さっこん. This gemination is a regular feature of Japanese phonology.

Key compounds using the サク reading:

• 昨日さくじつ (sakujitsu) — yesterday (formal, written)
• 昨年さくねん (sakunen) — last year
• 昨夜さくや (sakuya) — last night (formal)
• 昨晩さくばん (sakuban) — last evening / last night
• 昨今さっこん (sakkon) — nowadays, recently, these days
• 一昨日いっさくじつ (issakujitsu) — the day before yesterday (formal)
• 一昨年いっさくねん (issakunen) — the year before last (formal)

Kun'yomi (訓読み) — Native Japanese readings

昨 has no standard kun'yomi when used alone. The compound 昨日きのう (kinō) is a jukujikun (熟字訓) — an irregular reading assigned to the whole word, not derived from individual character readings. In daily speech, きのう is far more common than the formal さくじつ. Both are essential to know.

The same pattern applies further back in time: 一昨日おととい (ototoi) is the spoken form for the day before yesterday, and 一昨年おととし (ototoshi) for the year before last. Their formal on'yomi counterparts appear mainly in written Japanese.

Common Words & Compounds

昨 attaches to almost any time noun to express "the previous ~." Below, the most useful compounds are grouped by category.

Days and Dates

• 昨日きのう／さくじつ (kinō / sakujitsu) — yesterday (casual / formal)
• 一昨日おととい／いっさくじつ (ototoi / issakujitsu) — the day before yesterday
• 昨朝さくちょう (sakuchō) — yesterday morning (literary)

Nights and Evenings

• 昨夜さくや (sakuya) — last night (formal/literary)
• 昨晩さくばん (sakuban) — last evening / last night

Years and Seasons

• 昨年さくねん (sakunen) — last year
• 一昨年おととし／いっさくねん (ototoshi / issakunen) — the year before last
• 昨年度さくねんど (sakunendo) — last fiscal/academic year
• 昨春さくしゅん (sakushun) — last spring
• 昨夏さくか (sakuka) — last summer
• 昨秋さくしゅう (sakushū) — last autumn
• 昨冬さくとう (sakutō) — last winter

General and Abstract Use

• 昨今さっこん (sakkon) — nowadays, recently, these days (formal and written Japanese; refers broadly to the current era or period)

Example Sentences

Memory Tip

Look at the shape of 昨: the sun radical 日 on the right, and 乍 on the left — a component suggesting something brief and done. A sun that already crossed the sky and set. That's 昨日: yesterday, finished, gone.

For the reading, サク sounds close to "sock" in English. Think of yesterday as the day you balled up and tossed in the laundry — it's done, it's in the sock pile. Any time you spot 日 paired with 乍, that sun has already set.