Homeo- attaches to a root to form words expressing that something maintains a similar or constant quality, resembles something else, or follows a principle of “like affects like.” In physiology, it is most powerfully associated with the concept of equilibrium and self-regulation — the idea that living systems actively maintain a state of sameness (e.g., homeostasis, homeothermy). In genetics and developmental biology, homeotic refers to transformations where one structure becomes similar to or takes on the identity of another. In alternative medicine, homeopathy is founded on the principle that a substance causing symptoms in a healthy person can — in tiny doses — treat similar symptoms in a sick one (“like cures like”). The subtle difference between homeo- (“similar, like”) and the closely related homo- (“same, identical”) is that homeo- implies approximate or functional sameness rather than strict identity.
From Greek ὅμοιος (hómoios) — “like, resembling, of the same kind, equal, similar”
Related to Greek ὁμός (homós) — “one and the same” — from PIE root *sem- (“one; as one, together with”), also giving Latin similis (“similar”), semel (“once”), English same, seem, simple
The distinction: homos = identical/same; homoios = similar/like (a subtly broader, looser “sameness”)
Entered scientific English in the 19th century, Latinized from Greek homio-
Describing a mutation or gene causing one body part to develop in a similar pattern to another — e.g., legs growing where antennae should be in Drosophila
Homeotic gene
homeotic + gene
Master regulatory genes (Hox genes) that control body plan and segment identity
Homeobox (HOX)
homeo- + box (DNA sequence)
Highly conserved DNA sequence motif found in homeotic genes, responsible for controlling development across species