What is the difference between projects with normal cash flow and nonnormal cash flow?

Projects with normal cash flow have cash inflows that follow an initial investment outflow, typically resulting in a single change in the cash flow sign (e.g., negative to positive). In contrast, nonnormal cash flow projects involve multiple changes in the cash flow sign, meaning they can have multiple inflows and outflows over their lifespan. This distinction affects the project's risk and complexity, particularly when calculating metrics like net present value (NPV) or internal rate of return (IRR).