This document discusses concepts and variables in theory development. It defines concepts as abstractions based on characteristics of perceived reality that allow us to link observations and make generalizations. Concepts can range from abstract to concrete. Variables are factors that can be measured and vary between incidents or issues, and include independent, dependent, extraneous, and intervening variables. The independent variable affects the dependent variable, while extraneous variables also impact the dependent variable outside the independent variable. The intervening variable impacts the relationship between cause and effect under certain conditions.