Your great nephew and your granddaughter are second cousins to each other.
Fourth Cousins, twice removed
Your great great niece is the granddaughter of your niece or nephew. Your daughter and your niece or nephew are first cousins. Your daughter and your great great niece are first cousins, twice removed.
Your sister's grand daughter is your grand niece or great niece. You are her great aunt or great uncle.
Your nephew's granddaughter is your great great niece. Depending on whether you are male or female, you are that child's great great uncle or great great aunt.
You granddaughter is a great great niece of your aunt. Your aunt is your granddaughter's great great aunt.
Your child and your nephew are first cousins. Your granddaughter and your great nephew are second cousins. Your granddaughter and your great great nephew are second cousins once removed
An uncle's nephew and the uncle's child are first cousins to each other. The uncle's great granddaughter and the nephew are first cousins twice removed to each other.
Your nephew's son is your great nephew.
Your nephew's daughter's son is your great-great nephew. Your nephew's daughter is your great niece.
The child of your nephew is your great nephew (if a son) or your great niece (if a daughter).
Great neice
Your nephew's child is your great nephew (if a boy) or great niece (if a girl). You are his or her great aunt.