lisanduvus

Lisanduvus is a concept used in Estonian mathematics, statistics and related fields to describe a property of a quantity or system whereby the total value of a whole that can be decomposed into parts equals the sum of the values of its disjoint parts. It is typical for additive quantities and is often contrasted with non-additive or interactive effects.

In mathematics, a measure is additive: for any disjoint sets A and B, mu(A ∪ B) = mu(A) + mu(B). This extends to finite or countable collections. In probability theory, the expectation is linear: E[X + Y] = E[X] + E[Y]. The superposition principle in physics expresses a similar idea for linear systems, where outputs from independent inputs add.

Additivity is not universal. In many real-world systems, parts interact so the whole is not simply the sum of its parts; cross-terms or synergy can modify the total. In such cases one speaks of non-additivity or interaction effects.

Examples include simple counts (the number of objects in non-overlapping groups), masses or volumes in non-interacting materials, or the probability of independent, disjoint events when combined. In each case, lisanduvus describes a property that the whole can be determined by summing the contributions of its distinct components.

Related concepts include additivity, linearity, and the superposition principle. The term lisanduvus appears in Estonian-language texts on mathematics and the sciences to denote this additive property.