What type of cells have only one set of chromosomes?

Haploid cells are characterized by having only one set of chromosomes, which is denoted as "n." This means that in haploid cells, there is a single copy of each chromosome rather than paired copies. This is a crucial feature of cells involved in sexual reproduction, such as gametes (sperm and egg cells), which contribute to genetic diversity during fertilization.

In contrast, diploid cells contain two sets of chromosomes (2n), which are typical of somatic cells—most body cells in an organism. Polyploid cells have more than two sets of chromosomes, which is often seen in certain plants and can occasionally occur in some animal cells. Therefore, the distinction lies in the number of chromosome sets, making haploid cells unique in their single set of genetic material, fundamental for processes such as meiosis and the resultant formation of gametes.