Food loss and waste (FLW) has gained recognition as a threat to sustainable and healthy food systems because of potential negative impacts on food security, environmental, and livelihood outcomes. Despite increasing global efforts to reduce food loss and waste, there is still no single, harmonized terminology or definition. In this chapter, we summarize the current state of FLW definitions by examining major sources of data and how food loss and waste is defined according to an analytical framework specific to FLW. We then explore definitional elements to identify opportunities for harmonization and present a comprehensive and globally applicable FLW pathways framework. The pathways framework aims to provide clarity and consistency regarding FLW boundaries and destinations to align with sustainable food systems objectives.