The notion of dictionary presupposes the notion of ‘lexicon’. The lexicon is that component of the significative system of a language which represents the relation between signifier and signified of signs insofar as it is not subject to rules. It is the inventory of signs to which the speaker has a holistic, rather than analytic, access.

The relationship between the grammar and the lexicon in the significative system may be visualized as follows (see ‘Aufbau des Sprachsystems’ for a full explanation of the diagram):

The lexicon is, consequently, to be delimited against the grammar. The distinctive criterion is the holistic vs. analytic access taken by the language user. However, since a user may, in many cases, choose between the two modes of access, many linguistic units may be treated both in the lexicon and in the grammar.

The lexicon is heterogeneous in terms of the complexity levels of the units contained in it (the vertical dimension of the diagram). It is commonly assumed that the lexicon contains words; i.e., formally speaking, the lexemes of stems. In effect, however, the lexicon (just like the grammar) may contain material of any complexity from a proverb down to a suffix.

The semantic information of the lexicon is to be delimited against world knowledge. The lexicon is part of a language system; but not everything that we know is part of a language system. More on this in the section on ‘dictionary vs. encyclopedia’.