Copy number polymorphism refers to the variation in the number of copies of a particular genomic region present in the DNA of an organism. Synonyms that can be used interchangeably with the term copy number polymorphism include copy number variation, genomic duplication, gene amplification, and gene deletion. Copy number variation describes the differences in the number of copies of DNA segments between individuals, while genomic duplication refers to the presence of multiple copies of the same gene in the genome. Gene amplification indicates the replication of specific segments of the genome, while gene deletion is the loss of a specific DNA sequence from a chromosome. All of these terms describe the natural genetic variations observed in individuals and their role in the development of various diseases.