A brief review of the history of pedagogical content knowledge reveals various definitions and conceptualizations of the construct, as well as some conceptual problems. A new conceptualization--teacher pedagogical constructions--is offered to address some of the problems associated with PCK. Seven assertions that comprise the new conceptualization are presented, explained and defended. These are: (1) PCK represents personal and private knowledge; (2) PCK is a collection of basic units called teacher pedagogical constructions; (3) teacher pedagogical constructions result mainly from planning, but also from the interactive and post-active phases of teaching; (4) pedagogical constructions result from an inventive process that is influenced by the interaction of knowledge and beliefs from different categories; (5) pedagogical constructions constitute both a generalized event-based and a story-based kind of memory; (6) pedagogical constructions are topic specific; and (7) pedagogical constructions are (or should ideally be) labeled in multiple interesting ways that connect them to other categories and subcategories of teacher knowledge and beliefs. The proposed definition results from a reconceptualization of the nature of PCK as originally proposed, taking the results of major later studies and conceptualizations of PCK into consideration, appropriating new ideas about the structure of memory, and undertaking a reanalysis and presentation of data from a previous study. The article calls for viewing PCK as neither a subcategory of subject matter (subject matter knowledge for teaching) nor as a general generic form of knowledge. It presents a view of PCK as a collection of teacher professional constructions, as a form of knowledge that preserves the planning and wisdom of practice that the teacher acquires when repeatedly teaching a certain topic. Viewing PCK as a collection of TPCs, more precisely defining it, clarifying its relations to other knowledge and beliefs entities, and speculating about its development should facilitate future investigations of PCK. (Contains 4 figures.)