A semiconductor is a material that carries electricity in a controlled, in-between way. Silicon is the one inside almost every phone, computer, and memory stick. Metals conduct freely; insulators almost never do; semiconductors can be built into tiny switches. That is why the word is everywhere in Taiwan: “the semiconductor industry” means chip-making, not a pile of raw silicon. Though actually, calling it “semi” (half a conductor) is a school shortcut. The point is not that it is simply weaker than copper. The point is that we can tune it. Early devices used germanium; some lights and high-speed parts use other compounds. For a learner, keep one picture: the stuff chips are cut from, sitting between “flows easily” and “hardly flows”.