These black pants are typically referred to as "black pants" in Engpsh. The term is a straightforward, descriptive term that refers to pants that are colored black.
Here are a few example sentences using the term "black pants" in context:
"I always wear my black pants when I have a job interview."
"She paired her white blouse with black pants for a classic look."
"His black pants were torn and stained, so he decided to buy a new pair."
In these sentences, "black pants" is used as a noun to describe the type of clothing that the person is wearing.