Few kanji work as hard as 月. It is one of the very first characters you learn, yet it shows up in three quite different roles: the moon in the sky, a month on the calendar, and Monday in your weekly schedule. The good news is that this is not random. Each role tends to pair with a particular reading, and once you see the pattern, dozens of common words fall into place at once.
One kanji, three readings
月 has one kun’yomi and two on’yomi, and each maps loosely onto one of its meanings:
- つき (tsuki) — the native Japanese reading. This is the moon you can see: 月がきれいですね (tsuki ga kirei desu ne, “the moon is beautiful, isn’t it?”).
- ゲツ (getsu) — an on’yomi used in most month-related compounds and, crucially, in Monday: 月曜日 (getsuyōbi).
- ガツ (gatsu) — the other on’yomi, reserved almost exclusively for the names of the twelve calendar months: 一月, 二月, and so on.
Why two on’yomi? Japanese borrowed Chinese pronunciations more than once, centuries apart, and both readings stuck — each in its own set of words. You do not need the history to use them; you just need to know which words take which reading, and the groupings below do most of that work.
ゲツ: Monday and the moving months
月曜日 (getsuyōbi, Monday) is literally “moon-weekday.” Japanese weekday names follow a beautifully systematic pattern: 日 (sun) for Sunday, 月 (moon) for Monday, then 火 (fire), 水 (water), 木 (wood), 金 (metal/gold), and 土 (earth) for Tuesday through Saturday. Learn 月曜日 and you have a template for the entire week.
ゲツ also carries the “relative month” words — the months that move with you as time passes:
- 今月 (こんげつ, kongetsu) — this month
- 来月 (らいげつ, raigetsu) — next month
- 先月 (せんげつ, sengetsu) — last month. The first kanji, 先, means “previous, ahead” — the same 先 as in 先生 (sensei).
Notice the pattern: none of these words names a specific month. They point at a month relative to now, and they all read 月 as getsu.
ガツ: naming the calendar months
Japanese month names follow a single pattern: number + 月, read gatsu. 一月 (ichigatsu) is literally “month one,” 二月 (nigatsu) is “month two,” and the pattern carries through the whole year. Three months, marked ★ below, come with readings to watch:
| Month | Kanji | Reading | Romaji |
|---|---|---|---|
| January | 一月 | いちがつ | ichigatsu |
| February | 二月 | にがつ | nigatsu |
| March | 三月 | さんがつ | sangatsu |
| April ★ | 四月 | しがつ | shigatsu |
| May | 五月 | ごがつ | gogatsu |
| June | 六月 | ろくがつ | rokugatsu |
| July ★ | 七月 | しちがつ | shichigatsu |
| August | 八月 | はちがつ | hachigatsu |
| September ★ | 九月 | くがつ | kugatsu |
| October | 十月 | じゅうがつ | jūgatsu |
| November | 十一月 | じゅういちがつ | jūichigatsu |
| December | 十二月 | じゅうにがつ | jūnigatsu |
★ The three marked months use established readings of 四, 七, and 九 that differ from the counting words you may know best: 四月 is shigatsu (not yongatsu), 七月 is shichigatsu (nanagatsu is not the standard reading for July), and 九月 is kugatsu (not kyūgatsu). They stand out precisely because the everyday counting words 四 (yon), 七 (nana), and 九 (kyū) are so familiar.
This is the classic trap: 一月 read ichigatsu means January, but the similar-looking 一ヶ月 (ikkagetsu) means “one month” as a duration — and it switches back to getsu. “I studied Japanese for one month in January” would use both: 一月に一ヶ月勉強しました. Mixing up gatsu and getsu here is one of the most common reading mistakes at the beginner level, so it is worth saying the pair aloud a few times: ichigatsu = January, ikkagetsu = one month long.
つき: the moon you can see
When 月 stands alone as a noun, it is tsuki — the actual moon. The kun’yomi also survives in some compounds, especially older, more concrete words:
- 月見 (つきみ, tsukimi) — moon viewing. The second kanji is 見, “to see,” so the word is exactly what it looks like: “moon-seeing.”
- 毎月 (まいつき, maitsuki) — every month. A useful reminder that the reading groupings are tendencies, not laws: this month-related word uses tsuki, and まいげつ is also heard.
月見 deserves a short note, because it is the one place where this kanji touches a living tradition. In autumn, especially on the night called 十五夜 (じゅうごや, jūgoya — literally “fifteenth night,” the full moon of the old eighth lunar month), people display autumn grasses and round rice dumplings and simply look at the moon. For you as a learner, the vocabulary is the point: 月見 shows つき in action, and 十五夜 packs numbers, 月’s lunar-calendar history, and the kanji 夜 (night) into a single word. You will also meet 月見 on menus — 月見うどん is noodles topped with a raw egg, the yolk standing in for the full moon.
How to choose the right reading
A practical rule of thumb, good enough for almost everything at this level:
- 月 alone, or “moon” meaning? → つき
- Number + 月 naming a calendar month? → ガツ
- Almost everything else (Monday, relative months, durations with ヶ月)? → ゲツ
Exceptions like 毎月 (maitsuki) exist, but they are few — learn them as individual words when they appear.
Reading practice
Cover the answers and try reading these aloud:
- 月曜日に会いましょう。 — Getsuyōbi ni aimashō. (Let’s meet on Monday.)
- 今月は忙しいですが、来月は暇です。 — Kongetsu wa isogashii desu ga, raigetsu wa hima desu. (This month I’m busy, but next month I’m free.)
- 先月、日本に行きました。 — Sengetsu, Nihon ni ikimashita. (I went to Japan last month.)
- 一月と二月は寒いです。 — Ichigatsu to nigatsu wa samui desu. (January and February are cold.)
- 今夜は月見をします。 — Kon’ya wa tsukimi o shimasu. (We’re doing moon viewing tonight.)
Where to go next
Review the main 月 kanji page for stroke order, more example words, and related kanji. Then test yourself: every time you see 月 this week, pause and ask — moon, month, or Monday? Which reading is it, and why?