(music theory) A tuning system in which every interval (as a ratio of frequencies) is some exactly positive integral power of some smallest, other than the unison, base interval. In particular:

(mathematics, physics, potential theory) The partial differential equation (∂²𝜑)/(∂x_1²)+(∂²𝜑)/(∂x_2²)+⋯+(∂²𝜑)/(∂x_n²)=0, commonly written 𝛥𝜑=0 or ∇²𝜑=0, where 𝛥(=∇²) is the Laplace operator and 𝜑 is a scalar function.

The heuristic formula B=f(P,E), stating that behavior is a function of the person and their environment.

(chemistry) In polymer chemistry, a simple empirical formula that relates molecular weight to the glass transition temperature of a polymer system.

Any error common to all the observations of some individual; any tendency to error or prejudice due to the personal characteristics of some person for which allowance must be made.

(reaction kinetics) an equation expressing how the rate of a reaction depends on the concentrations of the reactants

(economics) The proposal that macroeconomic analysis be concerned with the theoretical consequences of optimizing behaviour by rational consumers, firms, and labourers, rather than with observable phenomena such as booms or slumps.

(chemistry) An equilibrium all participating substances of which are in the same phase.

(chemistry) an equilibrium of which not all participating substances are in the same phase

(figuratively) To become one of the factors that influences a situation or decision.