Final answer:
The term 'bilateral symmetry' refers to a biological concept where an organism or object can be divided into two symmetrical parts along a unique plane, resulting in distinct left and right halves.
Step-by-step explanation:
A term meaning "pertaining to both (two) sides" is bilateral symmetry. This biological concept refers to organisms or objects that can be divided into two symmetrical parts along a unique plane, also known as a mirror plane. Bilaterally symmetric organisms are characterized by having a body plan in which a single plane can cut from front to back, creating two mirror-image sides, with distinct left and right halves. This symmetry is a common feature in many animals and is associated with a highly developed level of mobility.
Examples of bilaterally symmetric organisms include humans, goats, and most vertebrates. These organisms have a single plane of symmetry, and whether the plane is cut from the top to the bottom or from front to back, it results in equal halves with a definite right and left side. This symmetry contrasts with asymmetry, where no such plane exists, and dichotomous divisions, which suggest a contrast between two things that are entirely different.