In this paper we will investigate how verbs are organized in the lexicon. It will be proposed that verbs are organized according to their meaning and the number of arguments they require. Every verb that receives an entry in the permanent lexicon must enter a slot in what we will term the Paradigmatic Structure (PDS); each PDS consists of three slots, Intransitive, Transitive, and Ditransitive. The PDS slots are fi rst fi lled by verb stems, which are morphologically the simplest form of the verb; at this point, a PDS can

have one, two, or all three slots fi lled depending on the existence of verb stems that share the appropriate meaning. To this are added morphological derivatives made up of a verb stem plus one or more derivational su xes. A morphological derivative can receive entry in the permanent lexicon if it is able to enter a PDS slot; such a slot, if vacant, is in the same PDS as the base (verb stem) of the derivative. If the appropriate slot is already fi lled by a verb stem, the derivative is blocked, and will never enter the permanent lexicon. The PDS thus acts as a fi lter for the permanent lexicon, letting some derivatives in while blocking others.