• 歯車はぐるま — gear
• 歯科しか — dentistry
• 虫歯むしば — cavity
• 歯並びはならび — alignment of teeth
• 義歯ぎし — artificial tooth, denture
• 乳歯にゅうし — baby tooth, milk tooth
• 歯石しせき — tartar (on teeth)

The shape of the kanji symbolizes teeth in the mouth. In older forms, it showed a row of teeth. Over time, it also came to represent something biting or grinding, including mechanical uses like "gear."

歯はを磨みがくことは 大切たいせつです。
Brushing your teeth is important.

この時計とけいは 歯車はぐるまで動うごいています。
This clock works with gears.