Iteroselectivity is observed when a limited number of repeating chemical transformations occurs in regard to the maximum number of reactive sites on a substrate. It is surprising that this concept was not properly named and defined earlier considering its common occurrence in simple reactions such as the alkylation of diols or aromatic substitutions. Moreover, the numerous recent studies successfully achieving iteroselective reactions through advanced methods clearly show a great interest of the chemistry community for this type of selectivity. We have now lifted the lack of definition and naming convention. Additionally, we provided means for measuring the degree of iteroselectivity through the calculation of iteromeric excess. The concepts described herein should lead to a better description of iteroselective processes in the literature and we hope that they will be helpful in other fields than organic and supramolecular chemistries including biochemistry and inorganic chemistry.