The daughter of your father's uncle is your father'sfirst cousin, and your first cousin - once removed. "Once removed" means a generation removed from you. Your parents and their siblings are a generation, you and your siblings are the next generation, your children are the next generation and so on.
Your daughter is your uncle's grand niece.
Great Uncle.
Since your uncle's sister is your aunt, her daughter would be your cousin, just as your uncle's daughter would be.
Your mother's brother is you uncle and your daughter's great uncle. Your daughter is his great niece.
their aunt or uncle
She is his great grandniece.
Your uncle's daughter is your cousin.
The father's son is the uncle of the son of the father's daughter.
There is no relation between you, and your biological Uncle's wife's sibling's daughter. Your Uncle's wife is technically an "Aunt in law", though as routine courtesy is simply called "Aunt". Her brother/sister, if your family and her family are that close, could be regarded as an "Uncle/Aunt in law", as a stretch. Thus the daughter of him/her could be thought of as a "cousin in law" to you. But this is all a matter of courtesy, there is no biological or legal relation.
I guess you will be her uncle. Consider this case.. You have a brother and he has a daughter.. Your daughter will be a sister in law to your brother's daughter.
Being your sister's brother or sister you would be an uncle or an aunt to her daughter.
Your nephew's daughter is your great niece and you are her great Aunt (or Great Uncle).Correction:Your nephew's daughter is your grand niece. You are her grand aunt or grand uncle.