Interestingly, iteroselectivity is not limited to reactions only modifying existing functions on a substrate but also applies to oligo-and polymerizations (Figure ). Indeed, a polymerization is an iterative reaction involving a repeating chemical transformation in which the reacting function is regenerated after each iteration. Therefore, a reaction leading to a major oligomer comprising a definite number of repeating units is iteroselective. Iteroselectivity is better suited to describe the selective formation of short oligomers while, for large polymers, the established concept of degree of polymerization is more appropriate. Indeed, large polymers are generally synthesized in batches of various lengths that are better described by their average length or weight rather than a precise number of iterations.