Meaning
透 conveys transparency, passage, and penetration — the quality that lets light, air, or perception move through without obstruction. Picture crystal-clear mountain water, a glass pane so clean it nearly disappears, or an insight sharp enough to cut straight to the core of a problem. In everyday Japanese, 透 spans both physical and figurative contexts: 光が透ける (light shines through a surface) at one end, 心まで透視される (being read all the way to one's innermost thoughts) at the other.
Structurally, 透 combines two elements. The outer component is 辶 (しんにょう), the movement radical — found in many characters involving travel, passage, and advance. The inner part is 秀 (しゅう), meaning "outstanding" or "excel." Together they suggest something that passes through with exceptional refinement, so pure that barriers cannot hold it back. Think of perfectly refined optical glass: only material clear to the point of flawlessness transmits light without bending or scattering a single ray.
At 10 strokes, 透 is a Jōyō kanji assigned to secondary school, which explains its more formal, literary feel. Less common than everyday kanji like 日 or 人, it nonetheless appears steadily across academic, medical, and aesthetic writing: 透明性 in political journalism, 透析 in medical reports, 透過 in physics and optics, 透き通る空 in poetry and travel writing.
Readings
On'yomi (音読み) — Chinese-derived readings
透 has one primary on'yomi reading, used in Sino-Japanese compound words (熟語, jukugo):
トウ (tō) — The Sino-Japanese reading, derived from historical Chinese pronunciation. In formal writing and compound nouns, this is almost always the reading to expect. When 透 appears inside a multi-kanji word, トウ is a reliable first guess.
- 透明 (tōmei) — transparent, clear. Literally "pass-through + bright." Applies to glass, water, and any material without opacity; also used figuratively for 透明な政治 (tōmei na seiji), open and accountable governance.
- 透視 (tōshi) — X-ray imaging, clairvoyance, seeing through barriers. Standard in medical contexts for radiographic imaging; extends figuratively to piercing insight.
- 透析 (tōseki) — dialysis. The procedure that filters blood through a semi-permeable membrane when the kidneys fail. Core vocabulary in healthcare.
- 透過 (tōka) — transmission, penetration of light, radiation, or sound through a medium. Central to physics, optics, and materials engineering.
- 浸透 (shintō) — permeation, infiltration, osmosis. Describes water seeping into soil, ideas spreading through a culture, or trends taking hold among a demographic.
Kun'yomi (訓読み) — Native Japanese readings
透 has three closely related kun'yomi readings, all built on the root su-. This root expresses thinning out, becoming sparse, or allowing passage through gaps. These forms appear in native Japanese words and poetic expressions.
す・く (su-ku) — An intransitive verb: to become transparent, to turn see-through, or to open up with gaps. It describes the state of something becoming visible through a gap or growing sparse enough for light to pass.
- 透き間 (sukima) — a gap, a crack, an opening between two things. Also used figuratively for a slot in a schedule (スケジュールの透き間) or a weak point in an argument.
- 透き通る (sukitōru) — to be crystal clear, translucent and beautiful. A poetic compound applied to clear skies, pure voices, and clean water.
す・かす (su-kasu) — The transitive form: to make something transparent, to hold up to the light, to let light pass through. An active, causative sense of creating transparency.
- 透かし彫り (sukashibori) — openwork carving, filigree. Gaps carved through material to form delicate patterns — a craft technique found in traditional woodwork and metalwork.
- 透かし (sukashi) — a watermark. The faint image embedded in banknotes and official documents, visible only when held to the light.
す・ける (su-keru) — An intransitive verb describing the state of being transparent or showing through. Used for sheer fabrics, tinted glass, or thin paper that reveals what lies beneath.
- 透けて見える (sukete mieru) — to show through, to be visible through a surface. Describes sheer clothing, translucent screens, or frosted glass where shapes are dimly visible.
Common Words & Compounds
The following compounds are grouped by theme:
Clarity and Transparency:
- 透明 (tōmei) — transparent, clear; literal for materials, figurative for openness in governance or relationships
- 透明感 (tōmeikan) — luminous clarity; common in beauty and fashion to describe glowing skin or a refreshingly pure quality
- 不透明 (futōmei) — opaque; figuratively, murky or uncertain, as in 不透明な将来 (an uncertain future)
- 半透明 (hantōmei) — semi-transparent, translucent; materials that admit some light but obscure what lies behind
- 透明性 (tōmeisei) — transparency as an abstract principle, especially in organizational or political discourse
Penetration and Permeation:
- 浸透 (shintō) — osmosis, infiltration, permeation; used in biology for osmosis and in social commentary for the gradual spread of ideas or trends
- 透過 (tōka) — transmission of light or radiation through a substance; core vocabulary in physics and materials science
- 透視 (tōshi) — X-ray imaging, clairvoyance; seeing through physical or metaphorical obstacles
Medical and Scientific:
- 透析 (tōseki) — hemodialysis; the life-sustaining procedure that filters waste from the blood of patients with kidney failure
- 透析患者 (tōseki kanja) — a dialysis patient
Physical Gaps and Openings:
- 透き間 (sukima) — a gap, crack, or space between things; also used for any opening in a schedule or defense
- 透かし彫り (sukashibori) — openwork carving or filigree; decorative art using intentional gaps
- 透かし (sukashi) — a watermark embedded in paper or security documents
Example Sentences
この水は透明でとてもきれいです。
Kono mizu wa tōmei de totemo kirei desu.
This water is transparent and very beautiful.
彼女の声は透き通るように美しかった。
Kanojo no koe wa sukitōru yō ni utsukushikatta.
Her voice was beautifully crystal clear.
窓から光が透けて入ってくる。
Mado kara hikari ga sukete haitte kuru.
Light shines through the window.
ドアの透き間から冷たい風が吹き込んでくる。
Doa no sukima kara tsumetai kaze ga fukikonde kuru.
Cold wind blows in through the gap in the door.
民主主義には政府の透明性が不可欠だ。
Minshushugi ni wa seifu no tōmeisei ga fukaketsu da.
Government transparency is indispensable for democracy.
彼は週に三回、病院で透析治療を受けている。
Kare wa shū ni sankai, byōin de tōseki chiryō wo ukete iru.
He receives dialysis treatment at the hospital three times a week.
SNSの普及によって、新しい文化が若者の間に浸透した。
SNS no fukyū ni yotte, atarashii bunka ga wakamono no aida ni shintō shita.
Through the spread of social media, new culture permeated among young people.
医師はレントゲンで患者の肺を透視した。
Ishi wa rentogen de kanja no hai wo tōshi shita.
The doctor examined the patient's lungs using X-ray imaging.
彼女の目には、私の嘘を透視する力があるようだ。
Kanojo no me ni wa, watashi no uso wo tōshi suru chikara ga aru yō da.
Her eyes seem to have the power to see straight through my lies.
秋の空は透明感があって、遠くの山の稜線まではっきり見える。
Aki no sora wa tōmeikan ga atte, tōku no yama no ryōsen made hakkiri mieru.
The autumn sky has a luminous clarity, and the ridgelines of distant mountains are clearly visible.
Memory Tip
Picture a supremely gifted traveler — 秀 (outstanding) walking an open road 辶 — so refined and pure that they pass through walls like a beam of light, leaving no trace. Completely transparent. 辶 gives you movement and passage; 秀 says the passage is exceptional, almost supernatural. Refined optical glass works the same way: material clear to the point of flawlessness lets light through without bending or scattering a single ray. Start with 透明 (tō-mei, transparent and bright) as your hook. When you spot 辶 wrapped around 秀, see that flawless beam cutting straight through solid matter — outstandingly transparent.