Meaning
介 revolves around one core idea: being in the middle. It describes someone or something positioned between two parties — a go-between, a mediator, an intermediary. A real estate agent connecting buyer and seller, a friend introducing two people at a party, a nurse caring for someone who cannot manage alone — all of these situations live inside this single kanji.
At just 4 strokes, 介 is visually direct. It depicts a person (人) flanked by two short strokes on either side, suggesting someone literally sandwiched between two parties. That picture carries the meaning without effort. Classified under the 人 (person) radical, it is a grade-8 Jōyō kanji that appears constantly in everyday vocabulary: introductions, caregiving, mediation.
In modern Japanese, 介 rarely stands alone as a word. Instead, it drives a large family of compound words (熟語) — from social introductions (紹介) to professional caregiving (介護) to diplomatic intervention (介入). Learning 介 gives you a foothold in all of them at once.
Readings
On'yomi (音読み) — Chinese-derived readings
介 has one primary on'yomi: カイ. This is the reading used in virtually all N2-level compound words.
- 紹介 (shōkai) — introduction (of a person or thing)
- 介護 (kaigo) — nursing care, caregiving for the elderly or disabled
- 仲介 (chūkai) — mediation, acting as a go-between
- 介入 (kainyū) — intervention, stepping in between parties
- 媒介 (baikai) — medium, vehicle through which something is transmitted
In any compound featuring 介, expect the meaning to involve some kind of intermediary or in-between role. That pattern holds reliably across the vocabulary.
Kun'yomi (訓読み) — Native Japanese readings
The kun'yomi readings appear less often in standard writing, but はさ(まる) is worth recognizing — it captures the physical sense of being squeezed or wedged between things.
- 介まる (hasamaru) — to be sandwiched between, to be caught in between
- 介 (suke) — an archaic reading found mostly in personal names
The reading すけ survives in samurai-era names like 「佐介」 or 「弥介」, carrying a nuance of "helper" or "assistant." Day-to-day, はさまる is the practical one — it turns up naturally whenever something gets stuck or wedged.
Common Words & Compounds
Since 介 appears in so many compound words, grouping them by theme makes them easier to absorb:
Introductions & Social Connection
- 紹介 (shōkai) — introduction (to a person or concept)
- 自己紹介 (jiko shōkai) — self-introduction
- 紹介状 (shōkaijō) — letter of introduction or referral
Care & Support
- 介護 (kaigo) — nursing care, elder care
- 介護士 (kaigoshi) — care worker, nursing aide
- 介抱 (kaihō) — tending to someone, nursing a sick person
Mediation & Intervention
- 仲介 (chūkai) — mediation, brokerage
- 介入 (kainyū) — intervention
- 介在 (kaizai) — being interposed, the existence of something in between
- 媒介 (baikai) — medium, vector (e.g., mosquitoes as disease vectors)
Set Phrases & Other Uses
- 介意 (kaii) — concern, minding something (formal/literary)
- 一介 (ikkai) — a mere (person), an ordinary individual (e.g., 一介のサラリーマン — just an ordinary office worker)
Example Sentences
友達に彼女を紹介してもらった。
Tomodachi ni kanojo wo shōkai shite moratta.
I had my friend introduce me to her.
自己紹介をお願いします。
Jiko shōkai wo onegai shimasu.
Please introduce yourself.
彼は仲介業者を通して家を買った。
Kare wa chūkai gyōsha wo tōshite ie wo katta.
He bought a house through a real estate agent.
祖父の介護のために、仕事を減らした。
Sofu no kaigo no tame ni, shigoto wo herashita.
I cut back on work to care for my grandfather.
政府は紛争に介入することを決めた。
Seifu wa funsō ni kainyū suru koto wo kimeta.
The government decided to intervene in the conflict.
蚊はさまざまな病気の媒介となる。
Ka wa samazama na byōki no baikai to naru.
Mosquitoes act as vectors for various diseases.
ドアに指が介まってしまった。
Doa ni yubi ga hasamatte shimatta.
My finger got caught in the door.
彼女は一介の学生にすぎないが、とても優秀だ。
Kanojo wa ikkai no gakusei ni suginai ga, totemo yūshū da.
She's just an ordinary student, but she's exceptionally talented.
介護士の仕事は大変だが、とてもやりがいがある。
Kaigoshi no shigoto wa taihen da ga, totemo yarigai ga aru.
Care work is demanding, but it's deeply rewarding.
Memory Tip
Picture a person (人) standing between two walls — that's exactly what 介 looks like. The two short strokes flanking the central figure represent the two sides, with the person right in the middle acting as a bridge. Think of a mediator holding out both hands: "Let me introduce you." That image of someone sandwiched between two parties covers every major use of 介 — caregiver, broker, introducer. Vietnamese learners have a bonus shortcut: giới thiệu (紹介, introduction) uses the same GIỚI sound, making the connection immediate.