What does colloidal mean?
Colloidal is an adjective describing matter in the colloidal state — a condition intermediate between true solutions and coarse suspensions. In a colloidal system, extremely fine particles, typically between one nanometre and one micrometre across, are dispersed evenly throughout a gas, liquid, or solid. Because these particles are small enough to resist gravity yet too large to dissolve, they remain suspended indefinitely: milk, fog, gelatin, and mayonnaise are all familiar colloids. The adjective appears most often in technical phrases such as colloidal suspension, colloidal solution, and colloidal particles, and it has entered everyday vocabulary through products like colloidal silver and colloidal oatmeal. Derived from the Greek word for glue, it reflects early chemists' impression that such substances were neither liquid nor solid but something intriguingly in between.
adjectiveRelating to or consisting of a colloid — a substance whose particles are dispersed throughout another medium, being larger than molecules but too small to settle out. Colloidal matter remains evenly suspended rather than dissolving or precipitating.
- Of or relating to a colloid: describing a state of matter in which fine particles are dispersed throughout a medium without dissolving or settling.
- (Chemistry) Characteristic of the colloidal state, exhibiting properties such as the Tyndall effect or Brownian motion.
"Milk is a colloidal suspension in which tiny fat droplets are dispersed throughout water."
"Gold can be prepared as a colloidal dispersion, producing ruby-red glass used in stained windows."
"The pharmacist recommended a colloidal oatmeal bath to soothe the child's eczema."
The word 'colloidal' literally means 'glue-like' — it comes from the Greek word for glue, because early chemists thought these strange in-between substances behaved like gelatin.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of colloidal
Colloidal derives from colloid, a term coined in the mid-nineteenth century by the Scottish chemist Thomas Graham, who took it from the Greek kolla, meaning glue, because gelatinous substances like starch and gelatin seemed to behave unlike ordinary crystalline materials. The same Greek root gives us collagen, named for the glue once made from animal connective tissue, and it is related to the Latin gluten, whence gluten and agglutinate. The adjective form arose naturally as chemists needed to describe systems exhibiting colloidal behaviour.
Related word forms
How colloidal is actually used
A technical term used chiefly in chemistry, physics, materials science, and medicine. In everyday contexts it appears most often in product marketing (e.g., colloidal silver, colloidal oatmeal), where it lends scientific authority. It functions almost exclusively attributively before a noun.
Easily confused with colloidal
Colloidal describes particle suspensions in chemistry, while colloquial describes informal, conversational language.