A haploid cell is a cell that possesses only a single copy of each chromosome, as opposed to a polyploid cell, which has multiple copies of homologous chromosomes.
An organism is said to be haploid if every cell in the organism is haploid. On the other hand, polyploid organisms do not necessarily have every cell with the same number of copies of homologs. For example, the somatic cells in most animals (including humans) are diploid, yet the gametes of these animals are haploid.
