This book is a thorough investigation of the semantics of two derivational affixes in English. The semantic structure of -age and -ery derivatives is analysed synchronically, on the basis of corpus data from the British National Corpus (BNC), and diachronically, on the basis of dictionary data from the Oxford English Dictionary (OED). To do this, the book introduces a new way of accounting for the semantic structure of derivational affixes: an adapted semantic map method. The study shows that the semantic structure of morphological categories can change significantly in a relatively short period of time, and that semantic maps can represent this change in a straightforward and accurate manner. They visualise the relations and interdependencies of the readings expressed by derivatives, which leads to a new understanding of the semantic Complexity of these categories but also highlights recurring polysemies.