Parasegment

Definition
noun, plural: parasegments
The fundamental unit of Drosophila development, which is made up of portions of two adjacent segments along the body of the embryo.
Supplement
The Drosophila larva consists of repetitive units that are involved in its development. The parasegment are called as such since the boundaries of parasegments do not match up exactly with the more perceptible external segments in the larva.
Word origin: Greek pará– (beside, alongside of, by, beyond) + segment.
Compare: segment.

See also: pair-rule gene.