Effect of a factor where the term is a factor raised to the power \(n\).
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 coefficients \({\hat \beta}_{11}\) and \({\hat \beta}_{22}\) are the second-order effects of \(T\) and \(c\) respectively.
See: interaction effect, main effect
Source:
PAC, 2016, 88, 407. 'Vocabulary of concepts and terms in chemometrics (IUPAC Recommendations 2016)' on page 416 (https://doi.org/10.1515/pac-2015-0605)