In this article, the author provides a brief introduction to a completely new theory in Semantics, Operational Semantics (OS), which concerns the meaning of the basic linguistic elements that are indispensable for any linguistic expression, i.e., the fundamental “grammatical” words and morphemes. Even if in the text there is no explicit reference to constructivism, OS could be relevant for constructivist approaches, since its fundamental presupposition is that the meanings of these linguistic elements are mainly sequences of elemental mental operations (amongst which those of attention play a key role) that are actively carried out by the subject.

Context: The constructivist approach to the definition (or analysis) of the fundamental meanings of language in Ernst von Glasersfeld’s work. Problem: Has this approach achieved better results than other approaches? Method: Review of a book chapter by von Glasersfeld that is devoted to the analysis of the concepts of “unity,” “plurality” and “number.” Results: The constructivist approach to the semantics of the fundamental elements of language (some of which are fundamental for sciences too) seems to have produced positive results; moreover these are in a field where other approaches have produced results that do not objectively seem satisfactory.

Key words: semantics, numbers, mental operations, attention, language