This book presents theoretical and experimental analyses of the nature of early verbs. At around the age of two years old, children start to combine words and produce their first verbs. Verbal items appear later than nouns in a child’s speech and refer to the relational concepts in the world that are represented in syntax through the argument structure. The central set of data investigated here is based on the analysis of the features of first verbal productions in Italian. Since the appearance of verbs implies the mastery of a mapping procedure between syntactic positions and semantic roles, the syntactic regularities found for each lexical verb class suggest that the relation at the syntax-semantics interface is well-established early on. The non-adult-like sentences are those which involve the mastery of the scope-discourse semantic interface or higher functional syntactic categories. The analysis of the delay in the production and comprehension of some constructions here uncovers some general characteristics of language acquisition devices.