"equations" - key terms from Wikipedia

algebraic equations
boundary layer equations
constitutive equations
cubic equations
difference equations
differential equations
diophantine equations
einstein field equations
equations
equations	are solved
equations	of motion
equations	of state
equilibrium equations
equilibrium equations	and symmetry
euler equations
evolution equations
field equations
fresnel equations
gradient equations
hamilton equations
lagrange equations
linear differential equations
linear diophantine equations
linear equations
mathematical physics equations
nonlinear differential equations
nonlinear equations
normal equations
number of equations
ordinary differential equations
parametric equations
partial differential equations
physical equations
polynomial equations
riemann equations
simultaneous diophantine equations
simultaneous equations
solutions of diophantine equations
stokes equations
system of equations
system of linear equations
theory of differential equations
these equations
three equations
tidal equations
transformation equations
transport equations
turbulent boundary layer equations
two equations
vacuum field equations