mittetühi

Mittetühi is an Estonian mathematical term meaning non-empty, used to describe objects that contain at least one element. It is most commonly applied to sets, sequences, and domains in functions, but can also refer to other structures with positive cardinality. The word is formed from mitte meaning “not” and tühi meaning “empty,” mirroring the English term non-empty.

In set theory, a set A is mittetühi if it is not the empty set Ø; equivalently, its cardinality is greater than zero (|A| > 0). The condition is often written as A ≠ Ø. The concept also appears in areas such as combinatorics, analysis, and computer science, where constructions or statements assume the existence of at least one element.

Examples: The set {5, 7} is mittetühi, while Ø is not. A singleton {a} is mittetühi for any a. In programming and data structures, a non-empty list or array is described as mittetühi in Estonian mathematical or theoretical texts.

See also: empty set, nonempty, cardinality.