This paper presents a work in progress within the ANR project Archaedyn, which concerns the development of an ‘alphabet’ designed to characterize and compare the evolution of the settlement pattern in several French microregions during the Roman period. The ‘alphabet’ is a composite indicator, built from 3 criteria relating to the quantitative, hierarchical and spatial evolution of the settlement pattern. The different combinations of these criteria form the characters of the ‘alphabet’. The evolution of the settlement system of each microregion between two periods can thus be written as a chain of characters. It is then possible to compare these ‘signatures’ of the different microregions through time. This indicator has a strong temporal dimension as it is designed in terms of stability/instability with the previous situation. Synthesising the evolutions of the settlement pattern on the long term, it is an efficient tool to identify major types of dynamics.