Effect of a factor where the term is a single factor.
Example: The yield of a synthesis is modelled in terms of the temperature \(T\) and concentration of a reactant \(c\): \[\hat Y = {\hat \beta}_{0} + {\hat \beta}_{1}T + {\hat \beta}_{2}c + {\hat \beta}_{11}T^{2} + {\hat \beta}_{22}c^{2} + {\hat \beta}_{12}Tc\] The estimated coefficient \({\hat \beta}_{1}\) and \({\hat \beta}_{2}\) are the main effects of \(T\) and \(c\) respectively.
See: interaction effect, nth-order effect
Source:
PAC, 2016, 88, 407. 'Vocabulary of concepts and terms in chemometrics (IUPAC Recommendations 2016)' on page 415 (https://doi.org/10.1515/pac-2015-0605)