What term refers to the number of sets of chromosomes in a cell?

The term that refers to the number of sets of chromosomes in a cell is "ploidy." Ploidy specifically indicates the complete set of chromosomes for a given organism and is commonly expressed as diploid (two sets), haploid (one set), triploid (three sets), and so forth. For example, humans are diploid organisms, which means they have two sets of chromosomes, one inherited from each parent.

Genotype refers to the genetic makeup of an organism with respect to a specific trait, while phenotype is concerned with the observable characteristics or traits that result from the genotype in interaction with the environment. Chromatin is the complex of DNA and protein found in the nucleus of eukaryotic cells, which organizes the DNA into a compact structure during cell division but does not designate the number of chromosome sets. Thus, ploidy is the correct term to define the number of chromosome sets within a cell.