Meaning
微 is not simply "small" — it describes things so slight they sit at the very boundary of perception: a barely audible sound, a trace amount of a substance, a nearly invisible tremor. In modern Japanese, 微 works mainly as a prefix element in compound vocabulary, adding a sense of "micro-," "slight," or "delicate" to whatever word it joins.
The left component is 彳, the "step" radical (Kangxi radical #60) — cautious, deliberate movement, like footsteps taken one at a time. The remainder of the character historically combined elements evoking something hidden, restrained, or difficult to detect. Together they produce the impression of a presence so minimal and tentative it barely registers: a faint rustle of leaves, a slight tremor underfoot, a breath of wind across still water.
At 13 strokes, 微 sits at the secondary school level in Japan's Joyo kanji system — beyond the six elementary grades. Its radical 彳 ties it to motion and passage, reinforcing the image of something that moves only imperceptibly. The vocabulary 微 unlocks spans a wide range: microbiology, calculus, gentle breezes, low-grade fevers, and the fine distinctions that make a situation difficult to call. You will encounter it regularly in academic papers, literary prose, and formal news writing.
Readings
On'yomi (音読み) — Chinese-derived readings
The on'yomi reading is ビ (bi), from Middle Chinese. It dominates compound words (熟語, jukugo) and appears most in academic, scientific, and formal written Japanese. The register is precise and clinical — right for contexts where the exact degree of smallness matters.
Key compounds using the ビ reading include:
- 微妙 (bimyō) — subtle, delicate, nuanced; used when something is difficult to evaluate clearly or has fine, hard-to-pin-down distinctions
- 微笑 (bishō) — a faint smile, a gentle smile; more restrained and elegant than the broader 笑顔 (egao)
- 微生物 (biseibutsu) — microorganism, microbe; the invisible life forms that underpin biology
- 顕微鏡 (kenbikyō) — microscope; literally "visible-micro-mirror," the instrument that makes the imperceptible seen
- 微熱 (binetsu) — slight fever, low-grade fever; clinically around 37.5°C–38°C in Japanese medical practice
- 微量 (biryō) — trace amount, minute quantity; critical in chemistry, nutrition, and pharmacology
Kun'yomi (訓読み) — Native Japanese readings
The kun'yomi reading is かすか (kasuka), used as かすかな (kasuka na) (adjective) or かすかに (kasuka ni) (adverb). Where ビ feels clinical, かすか is poetic and sensory — evoking sounds, lights, or presences just barely detectable at the threshold of awareness. It appears often in literary and poetic writing where mood and sensation carry the weight.
- 微かな音 (kasuka na oto) — a faint sound, a barely audible noise
- 微かな光 (kasuka na hikari) — a faint light, a dim glow at the threshold of visibility
- 微かに感じる (kasuka ni kanjiru) — to faintly sense, to barely perceive
微塵 (mijin, "particle" or "tiny piece") uses an archaic reading み for 微. In modern Japanese it is treated as a fixed phrase, not a productive reading. For N1, focus on ビ and かすか as the standard readings.
Common Words & Compounds
微 turns up across scientific, medical, meteorological, and everyday vocabulary. The compounds below are grouped by field.
Science & Technology
- 微生物 (biseibutsu) — microorganism, microbe; the foundation of microbiology
- 顕微鏡 (kenbikyō) — microscope; the instrument that brings the micro-world into view
- 微分 (bibun) — differentiation (calculus); the mathematics of infinitesimally small changes
- 微積分 (bisekibun) — calculus (differential and integral); a cornerstone of advanced mathematics
- 微細 (bisai) — minute, fine, microscopic; used in microelectronics, nanotechnology, and precision manufacturing
Weather & Physical Sensation
- 微風 (bifū) — a gentle breeze, a light wind; the kind that barely stirs the surface of water
- 微動 (bidō) — slight movement, tremor; used in seismology for barely perceptible vibrations
- 微光 (bikō) — faint light, a dim glow; the quality of light at dusk or dawn's edge
- 微振動 (bishindō) — microvibration, minute oscillation
Health & Medicine
- 微熱 (binetsu) — slight fever, low-grade fever; a key clinical term in Japanese healthcare
- 微量 (biryō) — trace amount; essential in pharmacology and nutritional science
- 微弱 (bijaku) — faint, weak, barely detectable; describes a pulse or electrical signal at the edge of measurement
Expression & Everyday Use
- 微妙 (bimyō) — subtle, nuanced; among the most common 微 compounds in daily speech, often signaling that something is tricky to assess
- 微笑 (bishō) — a faint, gentle smile; also seen as the verb 微笑む (hohoemu)
- 微調整 (bichōsei) — fine-tuning, minor adjustment; making small but precise corrections
- 微増 (bizō) — slight increase; commonly seen in news reports about statistics and economic data
- 微減 (bigen) — slight decrease; the statistical counterpart to 微増
Example Sentences
彼女は微笑を浮かべて答えた。
Kanojo wa bishō wo ukabete kotaeta.
She answered with a faint smile on her face.
微熱があるので、今日は学校を休みます。
Binetsu ga aru node, kyō wa gakkō wo yasumimasu.
I have a slight fever, so I will stay home from school today.
顕微鏡で微生物を観察した。
Kenbikyō de biseibutsu wo kansatsu shita.
I observed microorganisms through a microscope.
風が微かに感じられた。
Kaze ga kasuka ni kanjirareta.
A breeze could be faintly felt.
二人の意見には微妙な違いがある。
Futari no iken ni wa bimyō na chigai ga aru.
There is a subtle difference between the two people's opinions.
先月と比べて売上が微増した。
Sengetsu to kurabete uriage ga bizō shita.
Sales increased slightly compared to last month.
料理に微量の塩を加えると味が変わる。
Ryōri ni biryō no shio wo kuwaeru to aji ga kawaru.
Adding a trace amount of salt to a dish can change the flavor entirely.
地震計は微動でも感知できる。
Jishinkei wa bidō demo kanchi dekiru.
Seismographs can detect even the slightest tremors.
夜明けの微光が山の稜線を照らした。
Yoake no bikō ga yama no ryōsen wo terashita.
The faint light of dawn illuminated the mountain ridgeline.
彼の表情に微かな不安が見てとれた。
Kare no hyōjō ni kasuka na fuan ga mite toreta.
A faint hint of anxiety could be read in his expression.
Memory Tip
Picture someone taking tiny, careful footsteps — the left component 彳 (the step radical) literally shows cautious, deliberate movement. The person moves so slowly and gently that from a distance you can barely tell they are moving at all. Their presence is micro-small, their footfall inaudible. 微 pairs neatly with the English prefix micro-: both point to something reduced to its smallest, most delicate form. The sound ビ (bi) can cue the English word "brief" — something so brief and faint it almost disappears. When 微 appears in a compound, ask what is being made micro: a smile becomes a micro-smile (微笑), a fever becomes a micro-fever (微熱), an adjustment becomes a micro-adjustment (微調整).