perturbative

This term is primarily used within the highly specialized registers of theoretical physics, quantum mechanics, and advanced mathematics. It describes a specific methodology where a complex system is analyzed by adding a small, manageable disturbance to a known, simpler system. The connotation is one of approximation and incremental analysis rather than total systemic change.

In a technical context, it is frequently contrasted with non-perturbative methods. While perturbative approaches rely on the assumption that the disturbance is small enough to be treated as a correction, non-perturbative methods are required when the interaction is too strong for such approximations to remain valid.