A mortgage interest rate is the percentage of interest a lender charges on a home loan. It affects your monthly payment and the total cost of borrowing over time. While mortgage rates are a key part of personal finance and long-term budgeting, they have no direct connection to the definition of a 401(k). A 401(k) is a retirement-specific savings vehicle, not a borrowing tool or a type of loan. The two concepts differ not only in function — one accumulates savings, the other incurs debt — but also in time horizon and purpose. A mortgage interest rate impacts your housing costs, while a 401(k) helps build wealth for retirement. Mixing them up can blur the distinction between leveraging credit and building assets. Understanding both is crucial to a complete financial picture, but they serve entirely separate roles.