Ploidy is a term from genetics and cell biology. It is used to indicate the number of chromosome sets in a cell. Most eukaryotes have either one set (called haploid) or two sets (called diploid). Some other organisms are polyploid, they have more than two sets of chromosomes. Some amphibians are triploid, with three sets. The endosperm cells in the seeds of many plants are also triploid. Some kinds of trout or salmon have four sets ("tetraploid"). Other examples: