ABSTRACT
The derivation of information and knowledge from real-world datamakes it necessary to define properties that differentiate certain objects fromothers.Therefore, an explicit definition of a formal description of such objects is needed in a way that the natural distinction is preserved. It is obvious that theway an object is described depends on the context of interest. In the case of molecular structures, the chosen description of the same compound would certainly differ if a specific pharmaceutical target affinity or its experimental synthesis should be described. For this reason, literally thousands of molecular descriptors have been proposed covering all properties of interest. Thus, it is not the goal of this chapter to present an exhaustive list of descriptors but to provide a
detailed account on the most important types, principles, and algorithms.An encyclopedia that covers most of the important molecular descriptors can be found in Ref. [1].
