The pairing of the semantic and the syntactic properties of morphologically simple words is to a large extent non-arbitrary (contrary to what is the case for the pairing of their sound and meaning: cf. De Saussure 1916). This holds especially for the selectional properties of verbs; whether a verb is intransitive or transitive, for example, depends on the number of participants that are involved in the state of affairs denoted by the verb. This section highlights a number of approaches to the issue. Section 1.2.1 begins with the basic distinction between main and non-main verbs, and discusses a number of properties of these two main classes, while recognizing that there are verbs that show a somewhat hybrid nature. The remaining sections focus on the classification of main verbs: Section 1.2.2 discusses a number of properties that enter into the syntactic classification of verbs and proposes a partly novel syntactic classification that is based on the number and types of nominal arguments they take; Section 1.2.3 reviews a number of semantic classifications that build on and revise the four-way classification between events, activities, accomplishments and achievements originally proposed in Vendler (1957); Section 1.2.4, finally, addresses the question of how far it is possible to link the proposed syntactic and semantic classifications. Given that we cannot do justice here to the vast theoretical literature relevant for the syntactic and semantic classification of verbs and the linking between them, we refer the reader to the surveys of these topics in Van Hout (1996:ch.1) and Levin & Rappaport Hovav (2005).