In a chromosome pair connected by a centromere what is each individual chromosome called

Sister chromatid

Explanation:

Chromatid refers to one of the two identical halves of a duplicated chromosome. The two chromatids make up a duplicated chromosome and are referred to as sister chromatids. Centromere refers to a specialized constricted region of a chromatid. It serves to hold two sister chromatids of a chromosome together.

Each chromosome in prophase and metaphase consists of two sister chromatids. Sister chromatids separate from each other in anaphase and individual sister chromatid makes one daughter chromosome.