닭(dak)
A type of poultry bird mainly raised for meat and eggs
When to use
Chicken dishes, Poultry mention, Egg-related
The nuance
닭 refers to poultry birds and their meat or eggs, typically domestic chickens; it is not a waterfowl and is used mainly in contexts about chicken meat or eggs, unlike 오리.
오리(o-ri, ori)
A waterfowl living near water, raised or hunted for meat and feathers
When to use
Duck dishes, Waterfowl mention, Duck feathers
The nuance
오리 is a waterfowl living near water, used for duck meat or feathers, different from 닭 which is a land poultry; used in contexts about duck meat or waterfowl.