Trisome

Part of speech: noun

Definitions

1. A chromosome that appears in three copies within a cell rather than the usual pair, often resulting from an error in cell division
2. An extra chromosome found in triplicate in an organism's cells, which can cause developmental changes in genetic disorders
3. A single chromosome occurring as three copies in place of the normal two, typically arising during meiosis or mitosis

Etymology: "Trisome" is a compound built from "tri-", the Greek-derived prefix meaning "three," and "-some," a suffix that descends from an Old English word meaning "body" or "group." Put together they describe a chromosome that appears in threes rather than the usual pairs. The suffix "-some" is the same ending found in words like "wholesome" and "lonesome," where it originally carried the sense of a group or set. In "trisome," it marks a cell carrying a triple set of one particular chromosome, a condition that arises when an extra copy is present alongside the normal pair. Because "tri-" and "-some" are both productive building blocks, the term needed no special coinage beyond combining them in the field of genetics.