What does immutability mean?
Immutability means the quality of remaining unchangeable. The word is used when describing something that must, can, or should not be altered, such as a legal principle, a historical event, a mathematical value, or a data structure. Its connotation is usually one of permanence and stability, although the term can also suggest rigidity when applied to institutions, rules, or systems. In programming, immutability specifically means that an object's state or data cannot be changed after creation; programmers often copy immutable data rather than modify it directly. The word is especially common in legal, philosophical, scientific, and computing discussions. Its opposite, mutability, describes the capacity for change. Understanding immutability helps distinguish between processes that allow revision and those intended to preserve a fixed state for consistency, reliability, or protection against alteration.
nounThe quality of being unchangeable or impossible to alter. In computing, it refers to data or an object's state remaining fixed after creation.
- The quality or state of being unchangeable or impossible to alter.
- In computing, the property that data or an object cannot be modified after it has been created.
"The immutability of a contract provides both parties with a stable basis for agreement."
"The constitution's immutability has remained a central principle of the country's legal system."
"Using immutable data structures makes it easier for software to share information safely between processes."
Usually used as an uncountable noun; the plural is uncommon and normally reserved for distinct instances or examples of immutability.
"The study examines several different immutabilities in historical and legal thought."
Immutability is the principle that some things should remain unchanged—even when powerful new tools could otherwise alter them.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Where does immutability come from?
Immutability comes from the adjective immutable, which was borrowed from Latin immutabilis, meaning “not changeable.” That form combines the Latin prefix im- or in-, expressing negation, with mutabilis, derived from mutare, “to change.” The same root appears in English words such as mutable, mutation, and commute, in the latter through the Latin prefix com-.
Related word forms
How immutability is actually used
The noun is usually abstract and commonly occurs in legal, philosophical, scientific, and computing contexts. In computing, it is often contrasted with mutability; a mutable object can be changed after creation, whereas an immutable one cannot.
Easily confused with immutability
Immutability means being unable to change in principle, whereas immovability most often means being unable to move or be moved.
Immutability is the quality of not changing, while impunity is freedom from punishment or harmful consequences.