What do you call your uncle’s daughter?

Cousin or cousin.

My uncle and my mother are biological siblings. My uncle's children and I are cousins.

There are three types of cousins: First, cousins, that is, they are cousins ​​with their aunt's children.

The second is cousins, that is, the children of one's uncle are cousins.

The third is aunt and cousin, that is, the relationship with one's aunt's children is cousins. From a blood perspective, cousins, uncles, brothers and sisters are the same.