Among biblical wisdom literature the Book of Qohelet is well known for its idiosyncratic ideas. Also from a linguistic point of view, however, this book is a maverick in the Bible. Its language is difficult and puzzling. In most commentaries some linguistic pecularities of Qohelet have received due attention and more recently studies on the language of the book have appeared. The present monograph presents an inventory and a thorough study of those peculiarities in the format of a grammar: orthography, phonetics, morphology and syntax. Against some recent challenges the author defends the general consensus among critical scholars that the language of Qohelet is definitely late in the development of Biblical Hebrew. He accepts the presence of a number of Aramaisms, but rejects the Aramaic translation theory. Also Dahood's "Phoenician" theory is discussed in detail and rejected. The whole research is done in a continuous dialogue with linguistic and exegetical literature on Qohelet, as can be seen from the extensive bibliography. The second part of this study - on the vocabulary of Qohelet - has been published as Orientalia Lovaniensia Analecta 143.