Polish-Bulgarian confrontative grammar (PBCG) is the first, and so far the only one in the world, so extensive an attempt at semantic confrontation with a gradually developed interlanguage. It comprises nine tomes which have been published in twelve volumes. The decision has been taken that the description in the Grammar will lead in the direction from content to form. The semantic interlanguage allowed for the unfolding of two equivalent grammars: that of modern Bulgarian and that of modern Polish. The analysis of semantic categories employed in PBCG ensures a coherent confrontative description, regardless of whether the languages being described do or do not possess grammatical markers of the meanings. PBCG is a part of modern theoretical confrontative research based on the logical theory of quantification, the modern process theory called the Petri net, and on the theory of logical predicate-argument structures. Our study, thanks to the removal of a strict division between the grammatical and lexical levels, contributes many new observations about the phenomena under examination. Universal semantic categories, important for the description of language and unanalyzed so far, have been chosen here, viz. the basic categories of language such as tense, modality, definiteness/ indefiniteness and semantic case, none of which has as yet been exhaustively described in the academic grammars of Polish or Bulgarian.