epämuuttuvia

Epäämuuttuvia is a Finnish term formed from epä- meaning "not" and muuttuva meaning "changing." In ordinary Finnish usage the plural adjective epämuuttuvia describes things that do not change under a defined set of conditions or operations. The word is used in several disciplines, most commonly in mathematics, physics and computer science, to refer to invariants or immutable objects.

In mathematics and physics, epämuuttuvia often denotes invariants—properties or quantities that remain the same under a specified group of operations or transformations. Examples include geometric quantities that are preserved under isometries (such as lengths and angles), and more abstract invariants in linear algebra (such as the determinant or spectrum of a matrix under similarity transformations). In physics, invariants can include quantities like the spacetime interval in relativity or rest mass, which do not change under certain physical transformations. Constants, while related, refer to fixed numerical values, whereas invariants refer to properties that remain unchanged under a set of allowed changes.

In computer science and software development, epämuuttuvia often appears in the context of immutability. An immutable (epämuuttuva) object cannot be altered after it is created; operations that would modify it instead produce new objects. Imm mutability is a design choice that can improve reliability and thread-safety. Common examples are strings in several programming languages and data structures designed to be immutable by default in functional programming languages like Haskell or Erlang.

The term thus spans a range of disciplines, always signifying stability under specified conditions: either the unchanging nature of a property (invariants) or the unchangeability of an object’s state (immutability).