Lagrangian function, used to solve constrained minimization problems in optimization theory; see Lagrange multiplier
Lagrangian relaxation, the method of approximating a difficult constrained problem with an easier problem having an enlarged feasible set
Lagrangian dual problem, the problem of maximizing the value of the Lagrangian function, in terms of the Lagrange-multiplier variable; See Dual problem
Lagrangian, a functional whose extrema are to be determined in the calculus of variations
Lagrangian submanifold, a class of submanifolds in symplectic geometry
Lagrangian system, a pair consisting of a smooth fiber bundle and a Lagrangian density