noun
silicon (Si)
The chemical element silicon. Used in scientific and technical contexts.
ケイ素は半導体の材料として広く使われている。
Silicon is widely used as a material for semiconductors.
From 珪 (kei, 'silicon') + 素 (so, 'element'). The kanji 珪 was originally used for silicon, but modern Japanese prefers the katakana form ケイ素.