# Can a Lagrangian be defined for arbitrary physical systems? [duplicate]

For physical systems with conservative forces, we can define a potential function $$V$$, and a Lagrangian $$L=T-V$$. At first, I thought that lagrangian mechanics only applied to systems with conservative forces. But on wikipedia, it says that we can extend it to non-conservative forces. However, it doesn't show how to do it for arbitrary non-conservative forces. Can lagrangian mechanics be applied to arbitrary systems with arbitrary forces? If not, what is an example of a system where this is impossible?