short for hydroelectricity: electricity produced by the force of fast moving water such as rivers or waterfalls

Biofuels and wind power are promising technologies, along with small scale hydro and tidal power. 生物燃料发电、风能，还有小规模的水力发电和潮汐发电都是前景广阔的技术。

electricity supplied as a service to the public

Last year we cut our use of hydro and gas by 22%. 去年，我们将水电和天然气的使用量削减了22%。

Your hydro bill will not be affected in any way. 您的电费丝毫不会受到影响。

connected with or using the power of water

hydroponic (= a method of growing plants in water) 溶液培养（一种在溶液中培养植物的方式）

showing that hydrogen is present