nonmatches

Nonmatches is a plural term used across several fields to denote instances that do not meet a given criterion or do not align with a reference standard. The concept is typically paired with matches, forming a dichotomy used to classify and analyze data, events, or biological compatibility.

In data processing and record linkage, a nonmatch refers to a pair of records that are determined not to refer to the same entity after a comparison process. Nonmatches are used alongside matches as negative examples in model training, anomaly detection, and rule-based filtering. They contribute to metrics such as precision, recall, and the confusion matrix, helping to assess the accuracy of matching algorithms.

In sports and event scheduling, a nonmatch (or a non-played match) describes a scheduled contest that is not contested due to reasons such as forfeit, withdrawal, or cancellation. Depending on rules, the outcome may be recorded as a walkover or a bye, and the result can influence standings, points, and subsequent scheduling.

In medicine and transplantation, nonmatching can describe a lack of compatibility between donor and recipient, such as ABO or HLA mismatches. Compatibility testing and crossmatching aim to minimize nonmatches to reduce rejection risk and improve transplant success.

Outside these domains, nonmatches may also refer to any situation where observed data fail to align with a specified model, hypothesis, or expected pattern. The term emphasizes the absence of a match rather than the presence of a positive association.