Allelic expression variation: the expression pattern or level of the alleles in the hybrids is different from that in the parents. This can also refer to the expression of homoeologous loci in interspecific hybrids.

Allopolyploid: an organism or individual that contains two or more sets of genetically distinct chromosomes, usually by hybridization between different species.

Amphidiploid: synonymous to allopolyploid. Contains a diploid set of chromosomes derived from each parent. Strictly speaking, only bivalents are formed in an amphidiploid, whereas multivalents are formed in an allopolyploid.

Aneuploid: an individual in which the chromosome number is not an exact multiple of the typical haploid set for that species.

Apomixis: only one parent (usually female) contributes genes to the offspring.

Autopolyploid: a polyploid created by the multiplication of one basic set of chromosomes (in one species).

Circadian rhythms: A circadian rhythm is a roughly 24-hour cycle in the biochemical, physiological, or behavioral processes of living organisms, including plants, animals, fungi, and cyanobacteria. The term "circadian" comes from the Latin circa, "around", and diem or dies, "day", meaning literally "approximately one day". The study of biological temporal rhythms such as daily, tidal, weekly, seasonal, and annual rhythms is called chronobiology.

Epigenetics: non-Mendelian inheritance, heritable changes in gene expression without changes in primarily DNA sequences.

Gametic imprinting: the expression of a gene is dependent on its parental origin in the offspring.

Genomic shock: the release of genome-wide chromatin constraints of gene expression, including activation of transposons in response to environmental changes and genomic hybridization.

Heterosis: the greater vigor of growth, survival, and fertility in hybrids than in the parents.

Homoeologs: chromosomes or genes in related species that are derived from the same ancestor and coexist in an allopolyploid.

Homologs: genes or structures that share a common evolutionary ancestor.

Homoploid hybrids: hybrids formed between different species, in some cases, resulting in a derivative hybrid species without a change in chromosome number.

Imprinting or genomic imprinting: unequal expression of maternal and paternal alleles in the offspring.

Nonadditive gene expression: the expression level of a gene in an allotetraploid is not equal to the sum of two parental loci (1 + 1 ≠ 2), leading to activation (>2), repression (<2), dominance, or overdominance.

Orthologs: chromosomes or genes in different species that have evolved from the same ancestor.

Paralogs: two or more genes in the same species that share a single ancestral origin.

Paramutation: heritable changes in gene expression induced by allelic interactions.

Ploidy: the number of basic chromosome sets.

Polyploid: an individual or cell that has two or more basic sets of chromosomes.

X-chromosome inactivation: during mammalian development, the repression of one of the two X chromosomes in the somatic cells of females as a method of dosage compensation