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-ploid

Also ‑ploidy.

The number of sets of chromosomes in a cell.

From haploid and diploid (see text).

The two oldest forms are haploid (Greek haploos, single), of a cell or nucleus that has a single set of unpaired chromosomes, and diploid (Greek diplous, double), containing two complete sets of chromosomes, one from each parent. They were formed using the ending ‑oid, but the last two letters of the Greek stems became attached to it to make a new ending.

Other examples are triploid, containing three homologous sets of chromosomes; tetraploid, containing four; hexaploid, containing six; polyploid, containing more than two homologous sets of chromosomes; aneuploid (Greek an‑, not, plus eu‑, well, good), having an uneven number of chromosomes.

The state of having such chromosome arrangements is expressed by ‑ploidy: aneuploidy, polyploidy, triploidy.