silicon (Si)
The chemical element silicon. Used in scientific and technical contexts.
Silicon is widely used as a material for semiconductors.
ケイ素 is the chemical element silicon (Si) itself, whereas シリコーン is a man-made polymer produced from silicon.
Standard modern spelling for silicon, using katakana for the element name.
Older kanji form; still seen but less common than ケイ素.
Rarely used kanji form.
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.