The verbs of the 'to be'-group, also called verba substantiva, belong to the most enigmatic phenomena of the human language. Combining a distinct suppletivity of their conjugational forms in most languages with a striking semantic and functional ambiguity, as well as unique syntactic capabilities, they form a very specific class of linguistic entities. They can be referred to, without exaggeration, as one of the conceptually gravest and most symptomatic language formations. Typologically, the be-verbs demonstrate, on the one hand, a set of similar features in almost every language, which is...