What does chromosome mean?
A chromosome is one of the thread-like structures found in the nucleus of nearly all living cells, composed of DNA tightly coiled around proteins. Chromosomes carry genes — the instructions that determine an organism's traits and guide its development and functioning. Humans normally have twenty-three pairs, inheriting one set from each parent, including the X and Y chromosomes that influence biological sex. The word entered English in the late nineteenth century, coined from Greek roots meaning 'color' and 'body', because early scientists could observe these structures only by staining cells with dyes. Today 'chromosome' appears constantly in genetics, medicine, and popular science writing, especially in discussions of inherited conditions such as Down syndrome, which involves an extra copy of chromosome 21, and in fields like prenatal testing and evolutionary biology. Precise and technical, it is nonetheless familiar to general readers.
nounA thread-like structure of nucleic acids and protein found in the nucleus of most living cells, carrying genetic information in the form of genes.
- A thread-like structure in the cell nucleus consisting of DNA and protein that carries genetic information in the form of genes.
"Humans typically have twenty-three pairs of chromosomes in every cell nucleus."
"Down syndrome results from an extra copy of chromosome 21."
"In many species, the sex chromosomes determine whether an individual develops as male or female."
Regular plural. Often used with numerals or quantifiers when discussing karyotypes and species comparisons.
"Fruit flies have four pairs of chromosomes."
The word 'chromosome' literally means 'colored body' — it was named because scientists could only see these structures under a microscope after staining them with dyes.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of chromosome
The word 'chromosome' was coined in German as 'Chromosom' by the anatomist Wilhelm von Waldeyer-Hartz in 1888, building on earlier descriptions of the stained nuclear threads. It derives from the Greek 'chrōma' meaning 'color' and 'sōma' meaning 'body', reflecting how these structures became visible only when dyed with stains. Related English words sharing these roots include 'chromatic' and 'chromatography' (from 'chrōma') and 'somatic' and 'psychosomatic' (from 'sōma').
Related word forms
How chromosome is actually used
The term is scientific and neutral in register, used widely in biology, medicine, genetics, and journalism about health and inheritance. It is countable and takes a standard plural.
Easily confused with chromosome
Chromatin is the uncoiled mass of DNA and proteins filling the nucleus, whereas a chromosome is the distinct, condensed structure that chromatin forms during cell division.
A gene is a single segment of DNA encoding a trait, while a chromosome is the larger structure containing many thousands of genes.