Hydroelectricity is the electricity you get from water power — the current that leaves a hydroelectric plant and goes into the wires. Hydroelectric is the adjective (a hydroelectric dam); this is the noun (the energy itself). News and textbooks switch between “hydroelectric power” and “hydroelectricity,” and in ordinary talk they are very close. Strictly, this word is the electricity. It sits next to wind and solar as one kind of renewable power. Same real picture as hydroelectric: dams, falling water, turbines. Same caution too: cleaner at the chimney than coal, but a dam is still a huge change to a river.

水力發電（指發出來的電；口語「水電」多半指水費電費或水電工）