substitutie

Substitutie is a term used in several disciplines to denote the replacement of one element by another according to a defined rule or mapping. The overarching idea is that the substitute performs a similar role within a system as the element it replaces.

In mathematics and logic, substitution involves replacing a variable with an expression or another variable. It is used to solve systems of equations by expressing one variable in terms of another and substituting into the remaining equations, or to perform calculus substitutions such as u-substitution to simplify integrals. For example, solving a system with x + y = 5 and 2x − y = 1 by substitution yields x = 2 and y = 3.

In chemistry, substitution reactions replace an atom or group in a molecule with another atom or group, often via nucleophilic or free-radical mechanisms. Examples include SN1 and SN2 reactions in organic chemistry.

In genetics, a substitution mutation is a single-base change in DNA or RNA that can alter codons and amino acids, potentially producing missense or nonsense effects.

In information theory and linguistics, substitution can refer to a cipher that replaces letters with other letters to conceal text, or to substitute one linguistic unit for another in discourse. Monoalphabetic and polyalphabetic ciphers are common subtypes in cryptography.

Across fields, substitution shares the core principle of replacement under a prescribed rule, with practical implications ranging from solving equations to transforming chemical reactivity, genetic coding, or encoding information.