This paper aims at discussing the usage of the definite article with common nouns in Ancient Greek (AG), based on a case-study of the noun ἡμέραις (hēmerais/day.dat.pl) in epigraphic inscriptions. We propose that the use of the article in the inscriptions can be accounted for by the grammaticalization of identifiability (Lyons, 1999). Given that the article appeared in AG through the grammaticalization of the demonstrative (Roberts; Roussou, 2003), we postulate that its use began as a marker for contexts in which the referents of the nouns were identifiable by their description. Diachronically, and during the time span of our corpus (containing inscriptions from V BC to III AD), the language has formalized some contexts as arthrous, to be marked as definite – starting from the prototypically identifiable ones –, and some as anarthrous. Namely, anaphoric nouns or nouns modified by qualifying adjuncts are always arthrous, even when the referent is not properly identifiable, while quantifying adjuncts occur with nouns that are anarthrous. Consequently, the distribution of the presence and absence of article did not happen evenly throughout the variants of AG: only Gortyn’s dialect marks with an article nouns that do not have either a qualifying modifier or anaphor, but only quantification. The first section presents the studies on the definiteness of AG. The second section discusses instances in which the nominal heads have modifiers. The third section analyses the occurrences in which the noun is arthrous only with a cardinal number as modifier, and the fourth gathers the conclusion of the analysis.