The object of this research is the systematic and formal description of Modern Greek fixed and semi-fixed adverbs, abbreviated here to fixed adverbs (i.e. κέζα ζηα άγξηα κεζάλπρηα/in the dead of night, ην κήλα πνπ δελ έρεη άββαην/in a month of Sundays). Our goal is to obtain the most exhaustive and explicit description in the prospect of the automatic analysis of Greek language. Our framework is the Lexicon-Grammar methodology (M. Gross 1975, 1990a), based on the Transformational Grammar principles defined by Zellig S. Harris. This framework has provided us with an adequate model for the formal and systematic description of natural language. Our study is organised into five parts. The first part gives an overview of the two core notions pr...