The purpose of this paper is to offer an explanatory account of the differences in terms of categorial feature parameter in Old English (OE) and Present-day English (PE). It has been known that OE is different from PE in three things; verbal inflection, the word order of subordinate clause and matrix clause. Firstly, OE has rich verbal inflections which are listed as the inflected form in the lexicon while PE has poor verbal inflections which are the combined form of a root and inflections in the syntax. Secondly, the word order of the OE subordinate clauses is either OV or VO order while that of the PE subordinate clauses is rigid VO order. Lastly, the matrix order of OE clauses shows V2 phenomena in the affirmative while that of PE exhibits no V2 in the affirmative. In this paper these three differences between OE and PE are attributed to whether the category feature of T and V is specified or not in the syntax. Thus it is concluded that the category feature of T and V in OE is specified in the syntax whereas that of T and V in PE is not specified, which shows the differences in verbal inflections and the word order in subordinate and matrix clauses between OE and PF. (Youngsan University)