What does atactic mean?
Atactic is an adjective meaning lacking order, regular arrangement, or coordination. Its dominant modern use is in polymer chemistry, where it describes chains in which substituent groups are attached in a random orientation rather than following a consistent pattern. This randomness prevents the molecules from packing into crystals, making atactic polymers such as atactic polypropylene softer and less structurally useful than their stereoregular counterparts, known as isotactic and syndiotactic forms. A secondary, older sense appears in medicine, where atactic describes symptoms or movements characteristic of ataxia — the loss of full control over bodily motions. The word derives from Greek roots: the negative prefix a- combined with taxis, meaning arrangement or order, so it literally conveys the absence of arrangement. Because it belongs mainly to scientific registers, atactic rarely surfaces outside laboratory reports, textbooks, and patent literature, but within those fields it is precise, well established, and essential for distinguishing disordered molecular structures from orderly ones.
(of a polymer) having substituent groups arranged randomly along the chain rather than in a regular stereochemical pattern.
"The commercial resin contained a significant fraction of atactic material, lowering its melting point."
The most common sense in contemporary usage, found almost exclusively in chemistry.
relating to or affected by ataxia; showing a lack of muscular coordination.
"An atactic gait prompted the physician to order further neurological testing."
Less common today than the near-synonymous 'ataxic'; largely confined to older or specialist medical writing.
In polymer science, the difference between a cheap plastic byproduct and a high-performance material can come down to nothing more than whether the molecules line up — and 'atactic' is the word for when they don't.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of atactic
Atactic comes from the Greek elements a- ('not, without') and taxis ('arrangement, order'), literally meaning 'without arrangement'. It entered English through scientific usage in the nineteenth century, first in medical contexts relating to ataxia and later adopted by chemists for polymers lacking stereochemical regularity. It shares its root with words such as taxonomy, tactic, and syntax.
How atactic is actually used
Predominantly a technical term used in polymer chemistry and, to a lesser extent, medicine; rare in general conversation. In medical contexts it overlaps heavily with the more common adjective 'ataxic'.
Easily confused with atactic
Ataxic refers specifically to impaired muscular coordination caused by neurological dysfunction, whereas atactic more broadly denotes lack of ordered arrangement, including its technical chemical sense for polymers.