This study explores the development of children's knowledge of linguistic and pragmatic aspects of singular and plural in Italian, for definite articles (Experiment 1) and verbs (Experiment 2). Participants aged three to adult were asked to pick objects from two dishes, each with a different number of items on them (one vs. two), following the morphological information. Results show that children understand that singular forms refer to 'one' at about age four, whereas they understand that plural forms refer to 'more than one' when they are older than six. Moreover, children use singular and plural knowledge in appropriate relation with the referential context only when they are about six.