Technically, a wind turbine is a rotating machine that converts wind energy into mechanical energy. If the energy is used directly — to pump water or grind grain, say — the thing is generally called a windmill. If the energy is converted to electricity, wind turbine is preferred by authorities, and that’s what people in the business say. But laymen generally refer to both machines as windmills, and the Times here has used the terms more or less interchangeably.