The present paper aims to give an analysis of properties of the phytosociological language, which relates to the vagueness of some concepts in vegetation science. A translation of the simplest synsystematic propositions into possibility distributions has been proposed. Inferential relationships between sentences mentioned using the concept of semantic entailment have been reported. Sentences describing habitat requirements of syntaxa are in fact disguised conditionals; their paraphrases have been given the form of implication. Since these sentences include fuzzy predicates their meaning is a fuzzy relation. The latter may constitute the basis of prediction by means of the compositional rule of inference