Define Harmonic function and Harmonic conjugate.

Harmonic function: Any real valued function of x and y is said to be harmonic in a domain of the xy plane if throughout the domain it has continuous partial derivatives of the first and second order and satisfy the laplace equation.

Harmonic conjugate: The function v is said to be a harmonic conjugate of u if u and v are harmonic and u, v satisfy the C-R equations.