• 機械きかい — machine / machinery
• 器械きかい — apparatus / equipment
• 手械てかせ — handcuffs
• 械具かいぐ — mechanical tool
• 装置そうち — device / installation (related context)

A 形声文字 combining the radical 木 (tree / wood) with the phonetic element 戒 (warn, command). Originally linked to crafted wooden tools, it expanded to mean machinery and mechanical devices.