bilateral symmetry

Bilateral symmetry is a biological term describing organisms with a body plan where similar anatomical parts are arranged on opposite sides of a median axis. This means only one specific plane, passing through the center from head to tail, can divide the organism into two essentially identical halves.12

This type of symmetry is found in many higher animals, including humans, allowing for the distinction of a head (anterior) and tail (posterior) end, as well as a back (dorsal) and belly (ventral) side. While the external body may appear symmetrical, internal organs like the heart can disrupt perfect left-right equivalence in some species. This contrasts with radial symmetry, where parts are arranged around a central axis, and spherical symmetry, where any plane through the center divides the organism equally.34