Meaning
The kanji 歯 (ha/shi) primarily means 'tooth' or 'teeth'. This core meaning applies to both individual teeth and the entire set inside a mouth. Beyond its anatomical use, 歯 also appears in mechanical contexts, referring to a 'cog' or 'gear'. These mechanical parts resemble teeth in their function of interlocking and transmitting force, showcasing the kanji's versatility in describing anything with a tooth-like projection or function, whether biological or artificial.
Its origin is quite direct: 歯 is a pictograph. The older, more complex form 齒, which is the traditional Chinese character, clearly depicted teeth within a mouth. While the modern simplified Japanese 歯 is streamlined for easier writing, it still maintains this visual essence. You can imagine the top horizontal line as the gum line or the roof of the mouth, with the distinct lower elements forming a clear representation of a row of individual teeth. These might even hint at their roots or the slight gaps between them. It's an intuitive visual depiction of teeth arranged in a jaw, effectively capturing the essential form and function of our dental structures.
This kanji has 12 strokes, making it moderately complex to write, yet its components are logical once understood. It is officially designated as a Grade 3 kanji. Japanese children typically learn it during their third year of elementary school (小学三年生), highlighting its fundamental importance and commonality in everyday Japanese vocabulary.
Readings
On'yomi (音読み) — Chinese-derived readings
The on'yomi reading for 歯 is シ (shi). This reading is mainly used when 歯 forms part of a compound word, especially in more formal, medical, or technical terminology. Such compounds often combine 歯 with other kanji of Chinese origin, and you'll frequently encounter them in discussions about dentistry, specific dental conditions, or specialized types of teeth.
- 歯科 (shika) — dentistry, dental department. This term refers to the medical branch focused on diagnosing, preventing, and treating oral diseases.
- 義歯 (gishi) — denture, artificial tooth. These are prosthetic teeth designed to replace missing natural ones, restoring both function and appearance.
- 歯周病 (shishūbyō) — periodontal disease. A common inflammatory condition affecting the gums and the supporting structures around the teeth.
- 乳歯 (nyūshi) — baby tooth, milk tooth. These are the first set of teeth to appear in human development, which typically fall out to make way for permanent teeth.
- 永久歯 (eikyūshi) — permanent tooth. This refers to the second, definitive set of teeth that emerge after baby teeth are lost and are meant to last throughout adulthood.
Kun'yomi (訓読み) — Native Japanese readings
The primary kun'yomi reading for 歯 is は (ha). This is the most common reading when the kanji appears alone, directly meaning "tooth" or "teeth." It's also widely used in many everyday compound words, often paired with other native Japanese vocabulary. An important point is that when 歯 appears as the second element in certain compound words, its reading 'ha' can undergo rendaku (連濁). This is a common phonological change where the initial consonant becomes voiced (e.g., は becomes ば).
- 歯 (ha) — tooth, teeth. This is the simplest and most direct use of the kanji, referring to a single tooth or a set of teeth.
- 歯ブラシ (haburashi) — toothbrush. A common household item for maintaining oral hygiene.
- 前歯 (maeha) — front tooth/teeth. These are the incisors located at the front of the mouth, used for biting.
- 奥歯 (okuba) — molar, back tooth/teeth. These larger, flatter teeth are located at the back of the mouth and are primarily used for grinding food. Notice the rendaku from 'ha' to 'ba'.
- 歯医者 (haisha) — dentist. A common and informal term for a dental professional, combining 'ha' (tooth) with 'isha' (doctor).
Common Words & Compounds
Here's a selection of common words and compounds using 歯, categorized to show its diverse applications, from daily personal care to specialized technical and figurative expressions.
Dental Health & Care
- 歯医者 (haisha) — dentist. The medical professional specializing in oral health.
- 歯磨き (hamigaki) — brushing teeth; toothpaste. This term refers to both the act of cleaning teeth and the paste used for it.
- 歯ブラシ (haburashi) — toothbrush. The essential tool for daily oral hygiene.
- 虫歯 (mushiba) — cavity; decayed tooth. A common dental problem resulting from tooth decay.
- 歯垢 (shikō) — dental plaque. A sticky, colorless film of bacteria that constantly forms on teeth.
- 歯茎 (haguki) — gums. The soft tissue surrounding the base of the teeth.
Types & Structures of Teeth
- 前歯 (maeha) — front tooth/teeth. The incisors used for biting and cutting food.
- 奥歯 (okuba) — molar; back tooth/teeth. The larger teeth at the back of the mouth, essential for grinding.
- 親知らず (oyashirazu) — wisdom tooth. The last molars to erupt, typically in late adolescence or early adulthood.
- 入れ歯 (ireba) — dentures; false teeth. Removable prosthetics designed to replace missing teeth.
Figurative & Mechanical Use
- 歯車 (haguruma) — gear; cogwheel. A mechanical component with cut teeth that mesh with another toothed part to transmit power.
- 歯止め (hadome) — brake; curb; restraint. Figuratively, it means something that stops or prevents progress or growth.
- 歯が立たない (haga tatanai) — to be no match for; to be beyond one's grasp. This idiom literally means "teeth don't stand up," indicating that a task or problem is too difficult to handle or overcome.
Example Sentences
私の歯が痛いです。
Watashi no ha ga itai desu.
My tooth hurts.
毎朝歯を磨きます。
Maiasa ha wo migakimasu.
I brush my teeth every morning.
歯医者に行くのが少し怖いです。
Haisha ni iku no ga sukoshi kowai desu.
I'm a little scared to go to the dentist.
子供の乳歯がもうすぐ生え変わります。
Kodomo no nyūshi ga mō sugu haekawarimasu.
My child's baby teeth will be replaced soon.
この時計の中には小さな歯車がたくさんあります。
Kono tokei no naka ni wa chiisana haguruma ga takusan arimasu.
There are many small gears inside this clock.
歯周病の予防には、適切な歯磨きが不可欠です。
Shishūbyō no yobō ni wa, tekisetsu na hamigaki ga fukaketsu desu.
Proper brushing is essential for preventing periodontal disease.
その難問には、いくら考えても私の歯が立ちませんでした。
Sono nanmon ni wa, ikura kangaete mo watashi no ha ga tachimasen deshita.
No matter how much I thought about it, I couldn't get a handle on that difficult problem.
健康な歯を保つために、定期的な歯科検診が大切です。
Kenkō na ha wo tamotsu tame ni, teikiteki na shika kenshin ga taisetsu desu.
Regular dental check-ups are important to maintain healthy teeth.
Memory Tip
To remember the kanji 歯, imagine it as a stylized drawing of teeth inside a mouth. You can visualize the top part of the kanji—specifically the horizontal line and the two vertical strokes below it—as the upper gum line or the roof of the mouth. Below this, the distinct, structured lower elements clearly form the shape of individual teeth lined up in a row. These strokes can represent the biting surfaces and even the roots of the teeth. Picture a cross-section of a jaw, showcasing a strong, functional set of teeth, ready to chew. This visual connection directly links the kanji's form to its meaning, making it easy to recall.