Neumann Boundary Condition

A specification on the boundary of a domain that prescribes the value of the outward normal derivative of a function (or of a related flux) rather than the function's pointwise value.

A boundary condition that prescribes the normal derivative (flux) of the solution on the boundary, typically ∂u/∂n = h on ∂Ω, representing specified flow across the boundary.

A boundary condition for a partial differential equation that prescribes the value of the normal derivative (or normal component of a flux or traction) of the primary field on a domain boundary; commonly expressed as ∂u/∂n = g on ∂Ω for a scalar field u, where ∂/∂n denotes differentiation along the outward unit normal and g is a specified function (flux, heat flux, traction, etc.).