Lactam

From left to right, the above are general structures of β-lactam, a γ-lactam, a δ-lactam, and ε-lactam. Their common names are β-propiolactam, γ-butyrolactam, δ-valerolactam, and ε-caprolactam.

A lactam is a cyclic amide, formally derived from an amino alkanoic acid through cyclization reactions. The term is a portmanteau of the words lactone + amide.