agriculture, alternate, alternative, climate, compatible, ecologically, effect, energy, engine, environment, environmental, environmentally, fields, global, green, greenhouseeffect, nature, nonpolluting, oil, polluting, pollution, power, trees, turbine, warming, wheel, wind, windenergy, windengine, windfarm, windmill, windpower, windwheel, macromolecule, internal-combustion engine, production, motor, mill, woody plant, option, impurity, person, mechanism, machine, field, cultivation, farming, plant, lipid, heat engine, molecule, rotary engine, choice, peer, mood, commerce, transaction, surrogate, industry, tree, heating, environmental condition, machinery, consequence, outcome, stand-in, replacement
wind wheel