A Plain-Language Glossary of Budgeting Terms

Net Income

The amount of money you actually take home after taxes, Social Security, and any other payroll deductions have been removed. This is the number your budget should be built around — not your gross (pre-tax) salary.

Gross Income

Your total earnings before any deductions are taken out. Gross income is what appears in a job offer or contract, but it overstates the money you have available to spend and save.

Fixed Expenses

Recurring costs that stay the same from month to month, such as rent, a car payment, or a subscription at a set price. Because these amounts don't change, they are the easiest to plan for in a budget.

Variable Expenses

Spending that changes month to month, such as groceries, gas, utilities, or dining out. Variable expenses require more active tracking because the amounts fluctuate.

Discretionary Income

Money left over after you've covered essential needs like housing, food, utilities, and minimum debt payments. Discretionary income funds wants, hobbies, travel, and additional savings.

Cash Flow

The movement of money into and out of your accounts over a given period. Positive cash flow means more money is coming in than going out; negative cash flow means the reverse and often leads to debt accumulation.

Budget Deficit

The shortfall that occurs when your expenses exceed your income in a given period. Running a deficit typically requires drawing down savings or taking on debt.

Budget Surplus

The amount remaining when your income exceeds your expenses. A surplus gives you the opportunity to save, invest, or pay down debt ahead of schedule.

Sinking Fund

A savings category set aside for a specific, anticipated future expense — such as a car registration, holiday gifts, or a home repair. Small, regular contributions accumulate so the expense doesn't shock your budget when it arrives. Learn more in our guide to sinking funds.

Emergency Fund

A dedicated pool of savings intended to cover unexpected, urgent expenses — job loss, a medical bill, or a major repair — without going into debt. Most financial educators suggest three to six months of essential expenses as a general target range.

Zero-Based Budget

A budgeting method in which every dollar of income is assigned a purpose — spending, saving, or debt repayment — so that income minus all allocations equals zero. No money is left unassigned.

Pay Yourself First

A savings strategy in which a set amount is transferred to savings or a retirement account immediately when income arrives, before any spending occurs. The goal is to treat saving as a non-negotiable expense rather than an afterthought.