Duck is the common name for numerous species of waterfowl in the family Anatidae. Ducks are generally smaller and shorter-necked than swans and geese, which are members of the same family. Ducks are mostly aquatic birds, and may be found in both fresh water and sea water.

The word duck comes from Old English 'dūce' - 'diver'. A male duck is called a drake and the female is called a duck, or in ornithology a hen.

Ducks generally only have one partner at a time, although the partnership usually only lasts one year. Larger species and the more sedentary species (like fast-river specialists) tend to have pair-bonds that last numerous years.

More Info: en.wikipedia.org