素材
そざい · sozai · JLPT N1 · noun
raw material
🪵 素 = raw, plain + 材 = timber, material: raw materials to start with
The same idea covers subject matter: the raw stuff a story, essay, or talk is built from. 素材 is what you start with before shaping it into a finished product.
素 — silk 糸 + sheng 𠂹 (hanging threads)
Originally depicted raw, undyed silk hanging to dry, with the silk radical 糸 below and strands above. From this came the meaning 'plain, unadorned, white,' then extended to 'basic element' or 'plain/simple' in general. The 'vegetarian' sense developed later from the idea of plain, unembellished food.