Teacher working conditions (TWCs) have been linked to teacher retention and student learning. These connections make TWCs important to understand. However, the literature on TWCs lacks cohesiveness, with widely varying definitions, conceptualizations, and measures of TWCs. Contributing to this lack of cohesion is that there is no accepted construct definition delineating and defining what TWCs are and how to measure them. This dissertation fills a gap by developing a construct definition of TWCs through a two-step process. First, I developed a draft construct definition of TWCs through a systematic review and narrative synthesis of the literature, with a focus on defining TWCs narratively and organizing its components into a typology. Second, I employed the Delphi method, new to education policy research, to revise and validate the TWCs construct definition. Using this method, I administered two rounds of iterative questionnaires to teachers in North Carolina to obtain their feedback, suggestions, and input on the draft construct definition. Additionally, to address an overreliance on subjective measures in the literature, the questionnaire was designed to generate observable measures of TWCs. Questionnaire results informed revision to the construct definition, resulting in a definition and typology of TWCs that is research-based and teacher-vetted. This dissertation contributes a narrative definition, typology, and observable measures that clear a path for cohesive study of TWCs. Further, I identify components within the typology that teachers indicate are important and find that a widely used survey of TWCs does not address three of these important components. These findings have application in policy, research, leadership preparation, and for practitioners. [The dissertation citations contained here are published with the permission of ProQuest LLC. Further reproduction is prohibited without permission. Copies of dissertations may be obtained by Telephone (800) 1-800-521-0600. Web page: http://bibliotheek.ehb.be:2222/en-US/products/dissertations/individuals.shtml.]