日 — Day, Sun, Japan

Meaning

日 carries three meanings: 'day', 'sun', and 'Japan'. All three trace back to the same picture. Ancient forms of the character show a circle with a dot in the center — the sun in the sky. As the script standardized, the circle became a square and the dot became a horizontal line. That square with a line is what you write today.

With 4 strokes, 日 is a grade-1 kanji — taught to Japanese children in their very first year of school. It forms the foundation of dozens of characters related to time, light, and brightness. Get this one solid early.

Readings

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

ニチ (nichi): The dominant on'yomi. Appears in compound words for days of the week, day counts, and Japan itself.

日本にほん (nihon) — Japan
毎日まいにち (mainichi) — every day
日曜日にちようび (nichiyōbi) — Sunday
今日きょう (kyō) — today (irregular reading)

ジツ (jitsu): Less frequent, but appears in formal compounds about specific or official days.

休日きゅうじつ (kyūjitsu) — holiday, day off
元日がんじつ (ganjitsu) — New Year's Day
当日とうじつ (tōjitsu) — that very day

Kun'yomi (訓読み) — Native Japanese readings

ひ (hi): The core kun'yomi. Used when 日 stands alone or leads a compound, referring to the sun or a single day.

日ひ (hi) — day, sun
日差しひざし (hizashi) — sunlight
日帰りひがえり (higaeri) — day trip

-び (-bi): A voiced form of ひ, produced by rendaku (連濁). Appears when 日 follows another element in a compound — common in days of the week and special occasions.

日曜日にちようび (nichiyōbi) — Sunday (the final 日 reads び)
誕生日たんじょうび (tanjōbi) — birthday
記念日きねんび (kinenbi) — anniversary

-か (-ka): Used only for counting days or naming dates in the month. A holdover from classical Japanese number words.

二日ふつか (futsuka) — two days; the 2nd
三日みっか (mikka) — three days; the 3rd
十日とおか (tōka) — ten days; the 10th

Common Words & Compounds

Time and Calendar:

毎日まいにち (mainichi) — every day
今日きょう (kyō) — today
昨日きのう (kinō) — yesterday
明日あす (asu) — tomorrow
平日へいじつ (heijitsu) — weekday
休日きゅうじつ (kyūjitsu) — holiday, day off
誕生日たんじょうび (tanjōbi) — birthday
記念日きねんび (kinenbi) — anniversary
一日中いちにちじゅう (ichinichijū) — all day long

Sun and Light:

太陽たいよう (taiyō) — the sun (the celestial body)
日差しひざし (hizashi) — sunlight
日光にっこう (nikkō) — sunlight; also the city Nikkō
日没にちぼつ (nichibotsu) — sunset
朝日あさひ (asahi) — morning sun

Japan:

日本にほん (nihon / nippon) — Japan
日本語にほんご (nihongo) — Japanese language
日系にっけい (nikkei) — of Japanese descent

Other Common Compounds:

日記にっき (nikki) — diary
日程にってい (nittei) — schedule, itinerary
日課にっか (nikka) — daily routine
前日ぜんじつ (zenjitsu) — the day before
当日とうじつ (tōjitsu) — that day, the day in question

Example Sentences

毎日まいにち、日本語にほんごを勉強べんきょうします。

Mainichi, Nihongo o benkyō shimasu.

I study Japanese every day.

今日きょうは天気てんきがとてもいいですね。

Kyō wa tenki ga totemo ii desu ne.

The weather is really nice today, isn't it?

日本にほんに行いきたいです。

Nihon ni ikitai desu.

I want to go to Japan.

太陽たいようが東ひがしから昇のぼります。

Taiyō ga higashi kara noborimasu.

The sun rises in the east.

誕生日たんじょうびはいつですか。

Tanjōbi wa itsu desu ka.

When is your birthday?

先日せんじつ、友達ともだちと会あいました。

Senjitsu, tomodachi to aimashita.

I met a friend the other day.

三日みっかでこの本ほんを読よみました。

Mikka de kono hon o yomimashita.

I read this book in three days.

今日きょうの日程にっていはとても忙いそがしいです。

Kyō no nittei wa totemo isogashii desu.

Today's schedule is very busy.

日本にほんの文化ぶんかに興味きょうみがあります。

Nihon no bunka ni kyōmi ga arimasu.

I'm interested in Japanese culture.

Related Kanji

Memory Tip

Picture 日 as a window with sunlight coming through. The outer box is the frame; the horizontal line inside is a single ray of light. Sun shining through a window — that's your day. One image, two meanings covered.