Main Difference
The main difference between Lactone and Lactam is that the Lactone is a cyclic ester and Lactam is a family of chemical compound
Lactone
Lactones are cyclic carboxylic esters, containing a 1-oxacycloalkan-2-one structure (−(C=O)−O−), or analogues having unsaturation or heteroatoms replacing one or more carbon atoms of the ring.Lactones are formed by intramolecular esterification of the corresponding hydroxycarboxylic acids, which takes place spontaneously when the ring that is formed is five- or six-membered. Lactones with three- or four-membered rings (α-lactones and β-lactones) are very reactive, making their isolation difficult. Special methods are normally required for the laboratory synthesis of small-ring lactones as well as those that contain rings larger than six-membered.
Lactam
A lactam is a cyclic amide. The term is a portmanteau of the words lactone + amide.
Lactone (noun)
A cyclic intramolecular ester derived from a hydroxy acid.
Lactam (noun)
Any of a class of cyclic amides that are the nitrogen analogs of lactones, formed by heating amino acids; the tautomeric enol forms are known as lactims.