The sister of your father or mother is called your aunt. Likewise, you would call the wife of an uncle your aunt.
An uncle's partner is called aunt.
Your uncle or aunt's children are called your cousins.
Uncle
A parent, an aunt or an uncle.
Uncle is to aunt as father is to mother.
You are their uncle (if you are male) or aunt (female).
Well, here's the correlation you should follow: Your great uncle's wife = your great aunt, by marriage Your great aunt's sister = your great aunt, by marriage (think, your aunt's sister is also your aunt, just like your aunt's brother would also be your uncle!) Great aunt's grandson = distant cousin (think, your aunt's child is a cousin.)
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.
Sister-in-law describes a female. Brother-in-law describes a male.
The opposite relationship of uncle would be Niece or Nephew.(The opposite gender is aunt.)
The son of your aunt and uncle is your first cousin.
An uncle's spouse in the army is called an aunt-in-law. This term is used to specify the relationship between the uncle's spouse and the family members of the uncle. It is similar to other in-law relationships, such as mother-in-law or brother-in-law, indicating a familial connection through marriage.