This book mainly makes a detailed and somewhat technical investigation into Saussures concepts of difference, i.e. his difference-without-positive-terms, or opposition as he also calls, and systematicity along with other related concepts, in his discourse on language drawn mainly from the Course in General Linguistics (CGL). The outcomes of the research would demonstrate how difference and opposition are related, and also how systematicity is involved with the two; also how they function in the basic construction of language. The original motive of this book is that the researcher feels that difference is such a fundamental and even the most important concept in Saussures philosophy of language, yet it has received very little attention, and at present there is only a little correct construe of it. There is indeed a need for a serious investigation of his difference, to make it at least less obscure.