Specificity

Specificity is the quality of being clearly defined and limited to a particular subject, object, or range. In everyday language it signals precision. In scientific and analytical contexts, specificity denotes selectivity or a restricted target: a process, measurement, or system is described as specific when it predominantly affects or refers to a limited set of possibilities rather than a broad range.

In biology, specificity describes the preferential interaction between molecules or cells. Enzyme specificity refers to a preference for a specific substrate or chemical reaction; receptor–ligand and antigen–antibody interactions illustrate binding that occurs for particular molecular features. Immunological specificity underlies how immune receptors distinguish self from non-self and recognize particular pathogens, while developmental and signaling pathways often depend on highly specific cues.

In diagnostics, specificity is a statistical measure: the proportion of true negatives among all people who do not have the condition being tested for. High specificity minimizes false positives; it is commonly reported alongside sensitivity, the true positive rate. In other domains, specificity can mean the precision of a term in referring to a single entity or class, or the degree to which a query or description excludes alternatives. Across fields, specificity thus captures how narrowly defined or selective an entity or measurement is.