1dam 
/ˈdæm/ noun
plural dams /ˈdæm/ noun [count] : a structure that is built across a river or stream to stop water from flowing
▪ The government has plans to build a dam and flood the valley. ▪ There's a beaver dam [=a dam built by beavers] in the stream behind my house.
▪ The government has plans to build a dam and flood the valley. ▪ There's a beaver dam [=a dam built by beavers] in the stream behind my house.
— compare 3dam
