What is the difference between a chromatid and a chromosome?

a chromatid forms one part of a chromosome after it has coalesced for the process of mitosis or meiosis. during either process, the word "chromosome" indicates a pair of two exactly identical or "sister" chromatids joined at the central point of each chromatid, called the centromere.

a chromosome, by definition, has exactly one centromere. thus when sister chromatids are pulled apart by the mitotic spindle during anaphase - that is, when the centromere joining two sister chromatids splits into two centromeres - then each sister chromatid becomes an independent chromosome.

in non-gametic, non-dividing human cells, there are 23 pairs of chromosomes and thus 46 chromatids.

chromatid is a half of a chromosome.
like sister chromatids.

Chromosomes, consists of two sister chromatids