similarity
sameness
resemblance
correspondence
Relation between biological objects that resemble or are related to each other sufficiently to warrant a comparison.
homology
This broad definition encompasses all the working definitions proposed so far in the literature.
Similarity that results from common evolutionary origin.
homoplasy
Similarity that results from independent evolution.
analogy
homocracy
Homology and homocracy are not mutually exclusive. The homology relationships of patterning genes may be unresolved and thus may include orthologues and paralogues.
Similarity that is characterized by the organization of anatomical structures through the expression of homologous or identical patterning genes.
convergence
Convergence usually implies a notion of adaptation.
Homoplasy that involves different underlying mechanisms or structures.
parallelism
Can be applied for features present in closely related organisms but not present continuously in all the members of the lineage.
Homoplasy that involves homologous underlying mechanisms or structures.
parallel evolution
structural homology
idealistic homology
Homology that is defined by similarity with regard to selected structural parameters.
historical homology
true homology
cladistic homology
taxic homology
Homology that is defined by common descent.
phylogenetic homology
biological homology
Applicable only to morphology. A certain degree of ambiguity is accepted between biological homology and parallelism.
Homology that is defined by sharing of a set of developmental constraints, caused by locally acting self-regulatory mechanisms of differentiation, between individualized parts of the phenotype.
transformational homology
reversal
atavism
rudiment
Homoplasy that involves phenotypes similar to those seen in ancestors within the lineage.
reversion
syntenic homology
Structural homology that is detected by similarity in content and organization between chromosomes.
synteny
paralogy
Historical homology that involves genes that diverged after a duplication event.
syntenic paralogy
Paralogy that involves sets of syntenic blocks.
duplicon
paralogon
syntenic orthology
Syntenic homology that involves chromosomes of different species.
partial homology
fractional homology
mixed homology
modular homology
partial correspondence
percent homology
Structural homology that involves complex structures from which only a fraction of the elements that can be isolated are separately homologous.
segmental homology
protein structural homology
Structural homology that is detected at the level of the 3D protein structure, but maybe not at the level of the amino acid sequence.
non functional homology
pseudogene
Structural homology that involves a pseudogenic feature and its functional ancestor.
orthology
The term is sometimes also used for anatomical structures.
Historical homology that involves genes that diverged after a speciation event.
xenology
The term is sometimes also used for anatomical structures (e.g. in case of a symbiosis).
Historical homology that is characterized by an interspecies (horizontal) transfer since the common ancestor.
1 to 1 homology
one-to-one homology
Historical homology that involves two members sharing no other homologs in the lineages considered.
1:1 homology
1 to 1 orthology
1:1 orthology
one-to-one orthology
Orthology that involves two genes that did not experience any duplication after the speciation event that created them.
allogeny
Relationship between recognizably corresponding characters that occurs in two or more taxa and have different generative bases.
generative homoplasy
ohnology
homoeology
Paralogy that results from a whole genome duplication event.
in-paralogy
inparalogy
symparalogy
Paralogy that results from a lineage-specific duplication subsequent to a given speciation event.
out-paralogy
outparalogy
alloparalogy
Paralogy that results from a duplication preceding a given speciation event.
pro-orthology
1:many orthology that involves a gene in species A and one of its ortholog in species B, when duplications more recent than the species split have occurred in species B but not in species A.
semi-orthology
1:many orthology that involves a gene in species A and its ortholog in species B, when duplications more recent than the species split have occurred in species A but not in species B.
serial homology
homonomy
Iterative homology that involves structures arranged along the main body axis.
heterochronous homology
heterochrony
Biological homology that is characterized by changes, over evolutionary time, in the rate or timing of developmental events of homologous structures.
paedomorphorsis
Heterochronous homology that is produced by a retention in adults of a species of traits previously seen only in juveniles.
juvenification
pedomorphosis
peramorphosis
Heterochronous homology that is produced by a maturation of individuals of a species past adulthood, which take on hitherto unseen traits.
progenesis
Paedomorphosis that is produced by precocious sexual maturation of an organism still in a morphologically juvenile stage.
neoteny
Paedomorphosis that is produced by a retardation of somatic development.
juvenilization
mimicry
Convergence that results from co-evolution usually involving an evolutionary arms race.
1 to many orthology
co-orthology
one-to-many orthology
many to 1 orthology
Orthology that involves two genes when duplications more recent than the species split have occurred in one species but not the other.
1:many orthology
many to many homology
many-to-many homology
many:many homology
Historical homology that involves two members of a larger set of homologs.
1 to many homology
Historical homology that involves a structure that has no other homologs in the species in which it is defined, and several homologous structures in another species.
1:many homology
one-to-many homology
apomorphy
Historical homology that is based on recent shared ancestry, characterizing a monophyletic group.
synapomorphy
plesiomorphy
This term is usually contrasted to apomorphy.
Historical homology that is based on distant shared ancestry.
symplesiomorphy
deep homology
Used for structures in distantly related taxa.
Homocracy that involves morphologically and phylogenetically disparate structures that are the result of parallel evolution.
generative homology
homoiology
deep genetic homology
hemiplasy
Historical homology that is characterized by topological discordance between a gene tree and a species tree attributable to the phylogenetic sorting of genetic polymorphisms across successive nodes in a species tree.
gametology
Historical homology that involves not recombining and subsequently differentiated sex chromosomes.
chromosomal homology
Historical homology that involves the chromosomes able to pair (synapse) during meiosis.
many to many orthology
trans-orthology
many-to-many orthology
many:many orthology
trans-homology
Orthology that involves two genes that experienced duplications more recent than the species split that created them.
within-species paralogy
Paralogy that involves genes from the same species.
between-species paralogy
The genes have diverged before a speciation event.
Paralogy that involves genes from different species.
postdisplacement
Paedomorphosis that is produced by delayed growth of immature structures into the adult form.
post-displacement
hypermorphosis
Peramorphosis that is produced by a delay in the offset of development.
synology
Xenology that results, not from the transfer of a gene between two species, but from a hybridization of two species.
isoorthology
Orthology that involves functional equivalent genes with retention of the ancestral function.
tandem paralogy
Paralogy that is characterized by duplication of adjacent sequences on a chromosome segment.
iterative paralogy
serial paralogy
latent homology
Used for structures in closely related taxa.
homoplastic tendency
re-awakening
underlying synapomorphy
Parallelism that involves morphologically very similar structures, occurring only within some members of a taxon and absent in the common ancestor (which possessed the developmental basis to develop this character).
cryptic homology
apomorphic tendency
syngeny
Cannot be used when orthologous patterning gene are organizing obviously non-homologous structures in different organisms due for example to pleiotropic functions of these genes.
Homocracy that involves recognizably corresponding characters that occurs in two or more taxa, or as a repeated unit within an individual.
apparent orthology
The genes are actually paralogs but appear to be orthologous due to differential, lineage-specific gene loss.
1:1 paralogy
apparent 1:1 orthology
pseudoorthology
Between-species paralogy that involves single copy paralogs resulting from reciprocal gene loss.
pseudoparalogy
These genes may come out as paralogs in a single-genome analysis.
Xenology that involves genes that ended up in a given genome as a result of a combination of vertical inheritance and horizontal gene transfer.
equivalogy
This may include examples of orthology, paralogy and xenology.
Historical homology that involves functional equivalent genes with retention of the ancestral function.
interology
Historical homology that involves orthologous pairs of interacting molecules in different organisms.
functional equivalence
functional similarity
Similarity that is characterized by interchangeability in function.
iterative homology
Biological homology that involves parts of the same organism.
paraxenology
multiple xenology
Xenology that is characterized by multiple horizontal transfer events, resulting in the presence of two or more copies of the foreign gene in the host genome.
duplicate xenology
plerology
This phenomenon is usually due to gene conversion process.
Paralogy that is characterized by extra similarity between paralogous sequences resulting from concerted evolution.
homotopy
Theissen (2005) mentions that some authors may consider homotopy to be distinct from homology, but this is not the standard use.
Structural homology that involves structures with the same or similar relative positions.
homeosis
heterotopy
Biological homology that involves an ectopic structure and the normally positioned structure.
On a long term, it is hard to distinguish allopolyploidy from whole genome duplication.
Synology that results from allopolyploidy.
paramorphism
Iterative homology that involves two structures, one of which originated as a duplicate of the other and co-opted the expression of patterning genes of the ancestral structure.
axis paramorphism
regulogy
Historical homology that involves orthologous pairs of transcription factors and downstream regulated genes in different organisms.