妹 — Younger Sister

Meaning

The kanji 妹 means younger sister. It refers to a female sibling who is younger than the speaker — not just any sister. Japanese draws a firm line between older and younger siblings, so 妹 is never used for an older sister (that's 姉, ane).

妹 combines two elements: the radical 女 (woman, female) on the left, and 未 (not yet) on the right. Together they suggest a female who hasn't fully grown up — a younger sister. The component 未 originally depicted a tree that hasn't reached full height, always carrying the nuance of something still developing. You'll see the same idea in 未来 (mirai, future) and 未成年 (miseinen, minor).

Japanese children encounter this kanji in Grade 2 — early, because family words come up constantly in daily life. 妹 has 8 strokes and belongs to the 女 radical group, alongside 姉 (older sister), 姫 (princess), and 始 (begin).

You'll hear 妹 in self-introductions, family stories, and casual conversation alike. It's one of the first family kanji worth locking in at N4.

Readings

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

The on'yomi reading is マイ (MAI), from the historical Chinese pronunciation. It appears mainly in compound words and formal or literary contexts — not in everyday standalone speech.

姉妹しまい (shimai) — sisters (a pair of sisters)
義妹ぎまい (gimai) — sister-in-law (younger); a sister by marriage
令妹れいまい (reimai) — your esteemed younger sister; a formal way to refer to someone else's younger sister

Kun'yomi (訓読み) — Native Japanese readings

The kun'yomi reading is いもうと (imouto) — the native Japanese word for younger sister. This is by far the most common reading in daily speech. When talking about someone else's younger sister, use the polite form 妹さんいもうとさん (imouto-san) instead.

妹いもうと (imouto) — (my) younger sister
妹さんいもうとさん (imouto-san) — (your/his/her) younger sister (polite)
妹たちいもうとたち (imouto-tachi) — younger sisters; the younger sister and others

Common Words & Compounds

Family vocabulary

妹いもうと (imouto) — younger sister (one's own)
妹さんいもうとさん (imouto-san) — younger sister (someone else's, polite)
姉妹しまい (shimai) — sisters (as a pair or group)
兄妹けいまい (keimai) — brother and younger sister
義妹ぎまい (gimai) — sister-in-law (younger)

Formal and honorific forms

令妹れいまい (reimai) — your esteemed younger sister (formal/written)
舎妹しゃまい (shamai) — my humble younger sister (humble speech)

Idiomatic and extended uses

姉妹校しまいこう (shimai-kō) — sister school (a school with a formal partnership)
姉妹都市しまいとし (shimai-toshi) — sister city; twin city
姉妹品しまいひん (shimai-hin) — companion product; a related item in the same series

Example Sentences

わたしには妹いもうとが一人ひとりいます。

Watashi ni wa imouto ga hitori imasu.

I have one younger sister.

妹いもうとは今年ことし中学校ちゅうがっこうに入学にゅうがくしました。

Imouto wa kotoshi chūgakkō ni nyūgaku shimashita.

My younger sister started middle school this year.

妹いもうとの名前なまえはさくらです。

Imouto no namae wa Sakura desu.

My younger sister's name is Sakura.

田中たなかさんの妹さんいもうとさんはとても優しいやさしいですね。

Tanaka-san no imouto-san wa totemo yasashii desu ne.

Tanaka-san's younger sister is really kind, isn't she?

妹いもうとと一緒いっしょに買い物かいものに行きましたいきました。

Imouto to issho ni kaimono ni ikimashita.

I went shopping with my younger sister.

日本にほんと韓国かんこくは姉妹都市しまいとしの関係かんけいを結んでいますむすんでいます。

Nihon to Kankoku wa shimai-toshi no kankei wo musunde imasu.

Japan and South Korea have established a sister city relationship.

妹いもうとは毎日まいにちピアノを練習れんしゅうしています。

Imouto wa mainichi piano wo renshū shite imasu.

My younger sister practices piano every day.

姉妹しまいで力ちからを合わせてあわせて問題もんだいを解決かいけつした。

Shimai de chikara wo awasete mondai wo kaiketsu shita.

The sisters joined forces to solve the problem.

妹いもうとにプレゼントぷれぜんとを買ってかってあげるつもりです。

Imouto ni purezento wo katte ageru tsumori desu.

I plan to buy a present for my younger sister.

Related Kanji

物 — Thing, Object, Matter (Kanji N4)
弟 — Younger Brother, Junior (Kanji N4)
薬 — Medicine, Drug (Kanji N4)
族 — Tribe, Clan, Family Group (Kanji N4)
広 — Wide, Broad, Spacious (Kanji N4)
太 — Fat, Thick, Great (Kanji N4)

Memory Tip

Break 妹 into its two parts: 女 (woman/female) on the left, 未 (not yet) on the right. The logic reads as "a female who hasn't grown up yet" — a younger sister. 未 carries this same incomplete nuance in 未来 (mirai, future) and 未成年 (miseinen, underage): things still developing, not yet arrived. Picture a younger girl still growing up beside her older sibling — the "not yet" woman in the family.