"Diploid" means having two sets of chromosomes. The diploid number is the number of chromosomes in most cells except the gametes, which are haploid (containing only a single set of chromosomes). In humans, the diploid number is 46. In a diploid cell, the chromosomes of each pair carry the same genes.


The cells of angiosperms (flowering plants) and gymnosperms are also diploid. Algae and lower plants, such as ferns and mosses, have two generations in their life cycle, one diploid and the other haploid.


The term 'trisomic' describes a diploid organism that has three of one type of chromosome instead of two. Trisomy is the cause of several human genetic diseases, notably Down's syndrome.