Chaos is complete disorder: nothing where it should be and nobody in control. A kitchen at the end of a children's party, an airport when every flight goes at once, a meeting where six people talk over each other.
Say it with a hard K, KAY-oss, and KAY-otic for the adjective chaotic. It is a strong word: a messy desk is not chaos, a collapsed timetable with three hundred people stuck in a corridor is. Older writing uses chaos for the shapeless emptiness before the world was made, which is where the grand tone comes from. In maths and science it means something else entirely, naming systems that obey exact rules and still cannot be predicted, which is what chaos theory studies. There is no plural; chaos is one uncountable heap.
1nounchaosComplete disorder, in which nothing works as it should and no one is in control.
“The strike brought chaos to every port on the coast.”
synonyms: disorder, mayhem, havoc
2nounbehaviourBehaviour in a system that follows exact rules and still cannot be predicted.
“Weather is the standard example of chaos in a physical system.”
3nounshapelessThe shapeless emptiness or raw matter imagined to exist before the ordered world, in older writing.
“In the old poems the world is shaped out of chaos.”
Too few real examples of this word to estimate which sense is commonest.
chaos is a state of disorder.
Also accepted in games: disorder, mayhem
Early Modern English took chaos in the sense the original Greek word carried, and by the 16th century it named the primordial matter the world was made from. The everyday meaning, confusion and disorder, is 17th-century, and the technical sense in maths and science arrived only in the 1960s. Chaos also has a twin: gas, which reached English through Dutch, is the same word. It pushed out the native English word for muddle, dwolma, which nobody has missed.
Ancient Greek
χάος — vast chasm, void
English, today
chaos
Learned borrowing from Ancient Greek χάος (“vast chasm, void”). a doublet of gas, which was borrowed through Dutch. Displaced native dwolma. In Early Modern English, used in the sense of the original Greek word. In the meaning “primordial matter” from the 16th century. Figurative usage in the sense “confusion, disorder” from the 17th century. The technical sense in mathematics and science dates from the 1960s.
Etymology from Wiktionary, CC BY-SA