The role of the abstract triconsonantal root in the acquisition of Moroccan Arabic was investigated. Evidence from recorded speech samples of 32 Moroccan children between the ages of 3 and 6 is used to demonstrate that the abstract root plays a central role in both the nominal and verbal acquisition of the lexicon of Semitic languages and that the acquisition process follows a U-shaped developmental curve. A four-stage process for the acquisition of the Semitic lexicon is suggested, involving the use of patterns as amalgams, discovery of patterns, extraction of consonantal roots from patterns, and derivation of complex forms from basic forms. It is shown that the data fail to support Berman's (1981) assertions that the basic pattern is central in verbal derivation and that nouns are acquired as independent lexical items. Rather, verbal and nominal derivations are part of the same derivational process which has the morphological consonantal root as its central core. (RW)