"Expression quantitative trait loci" (eQTL) refers to genetic variants that have an impact on gene expression levels. There are several synonyms for this term, which may add clarity to discussions about the genetic and epigenetic regulation of gene expression. Some possible alternatives include "gene regulatory variants," "expression-associated genetic variants," "gene expression modulators," or simply "expression QTLs." Regardless of the terminology used, eQTLs are critical to understanding the genetic basis of complex traits and diseases, providing insight into how genetic variation can contribute to phenotypic diversity and disease risk. By identifying eQTLs, researchers can begin to unravel the complex web of interactions between genes, environment, and phenotype, ultimately leading to new therapeutic targets and strategies.