Glossary
Plain-language definitions of financial, health, math, and construction terms. AEO-friendly: optimized to be cited in AI overviews and answer engines.
Every definition here is written to be quotable, citable, and useful for AI assistants like ChatGPT, Perplexity, and Bing Copilot. Each entry includes the term, a short definition, a longer explanation, related calculators, and related terms. Updated quarterly by our editorial team.
Finance (20 terms)
APR (Annual Percentage Rate)
The yearly cost of a loan, expressed as a percentage, including most fees. Used when borrowing money.
Read full definition →APY (Annual Percentage Yield)
The yearly return on a deposit or investment, including the effect of compounding. Used when saving money.
Read full definition →Compound Interest
Interest calculated on the initial principal AND on the accumulated interest from previous periods. The engine of long-term wealth.
Read full definition →Simple Interest
Interest calculated only on the original principal, not on accumulated interest. Used in short-term and consumer loans.
Read full definition →Principal
The original sum of money borrowed or invested, not including interest. The base on which interest is calculated.
Read full definition →Amortization
Spreading loan payments over time so each payment covers both principal and interest, with the loan fully paid off at the end.
Read full definition →Equity
The current market value of an asset minus any outstanding debt against it. What you actually OWN of the asset.
Read full definition →ROI (Return on Investment)
A percentage that measures the gain or loss of an investment relative to its cost. Higher ROI = better investment.
Read full definition →CAGR (Compound Annual Growth Rate)
The mean annual growth rate of an investment over a specified period longer than one year, assuming reinvestment of returns.
Read full definition →IRR (Internal Rate of Return)
The discount rate that makes the net present value of all cash flows from a project equal to zero. Used in capital budgeting.
Read full definition →NPV (Net Present Value)
The difference between the present value of cash inflows and outflows over time. Positive NPV = profitable project.
Read full definition →Inflation
The rate at which the general level of prices for goods and services rises, eroding purchasing power. Measured by CPI.
Read full definition →Liquidity
How quickly an asset can be converted to cash without losing value. Cash is the most liquid asset; real estate is the least.
Read full definition →Diversification
Spreading investments across different assets to reduce risk. The only "free lunch" in investing.
Read full definition →Break-Even Point
The sales volume or revenue at which total costs equal total revenue. Above this, you make a profit; below, a loss.
Read full definition →Mortgage
A loan used to buy real estate, with the property serving as collateral. The most common long-term debt for individuals.
Read full definition →Down Payment
The upfront cash portion of a purchase, paid at closing. The remainder is financed through a loan or mortgage.
Read full definition →PMI (Private Mortgage Insurance)
Insurance required by lenders when the down payment is less than 20%. Protects the lender, not the borrower.
Read full definition →Rent vs. Buy
The financial decision between paying a landlord to occupy a home vs. taking a mortgage to own one. Each has different long-term costs.
Read full definition →CPI (Consumer Price Index)
A measure of the average change in prices paid by consumers for a basket of goods and services. The main inflation gauge.
Read full definition →Health & Fitness (9 terms)
BMI (Body Mass Index)
A numerical value calculated from weight and height that classifies adults as underweight, normal, overweight, or obese.
Read full definition →BMR (Basal Metabolic Rate)
The number of calories your body burns at complete rest, performing basic functions like breathing and circulation.
Read full definition →TDEE (Total Daily Energy Expenditure)
The total calories your body burns in a day, including all activity. The basis for diet planning.
Read full definition →Macronutrients
The three main nutrient groups the body needs in large quantities: protein, carbohydrates, and fat. The "macros."
Read full definition →Body Fat Percentage
The proportion of total body mass that is fat. A more accurate health metric than BMI for body composition.
Read full definition →VO2 Max
The maximum rate of oxygen your body can use during exercise, measured in mL/kg/min. A key fitness metric.
Read full definition →Heart Rate Variability
The variation in time between heartbeats, measured in milliseconds. A marker of recovery and overall health.
Read full definition →Resting Heart Rate
The number of times your heart beats per minute when you are at rest. A key indicator of cardiovascular fitness.
Read full definition →Lean Body Mass
Total body weight minus all body fat. Includes muscle, bone, water, organs, and connective tissue.
Read full definition →Mathematics (11 terms)
Standard Deviation
A measure of how spread out numbers are from their mean. Low = consistent, high = volatile.
Read full definition →P-Value
The probability of observing results at least as extreme as those observed, assuming the null hypothesis is true.
Read full definition →Mean (Average)
The sum of values divided by the count. The most common type of "average." Sensitive to outliers.
Read full definition →Median
The middle value in a sorted list. Half the values are above, half below. Robust to outliers.
Read full definition →Pythagorean Theorem
In a right triangle, the square of the hypotenuse equals the sum of the squares of the two legs: a² + b² = c².
Read full definition →Logarithm
The exponent to which a base must be raised to produce a given number. log(100) = 2 means 10² = 100.
Read full definition →Exponent
A number that indicates how many times a base is multiplied by itself. 2³ = 2×2×2 = 8.
Read full definition →Permutation
An arrangement of items in a specific order. Number of ways to arrange n items = n! (n factorial).
Read full definition →Combination
A selection of items where order does NOT matter. C(n,k) = n! / (k!(n-k)!).
Read full definition →Probability
A measure of how likely an event is, between 0 (impossible) and 1 (certain). Often expressed as a percentage.
Read full definition →Pi (π)
The ratio of a circle's circumference to its diameter. Approximately 3.14159, an irrational number.
Read full definition →Construction & Geometry (6 terms)
Area
The amount of 2D space inside a shape, measured in square units (m², ft², acres, hectares).
Read full definition →Volume
The amount of 3D space inside a shape, measured in cubic units (m³, ft³) or in liters/gallons.
Read full definition →Perimeter
The total distance around the outside of a 2D shape. Measured in linear units (m, ft).
Read full definition →Circumference
The perimeter of a circle — the total distance around it. C = 2πr, or C = πd.
Read full definition →Slope
The steepness of a line, calculated as rise over run. Slope = (y₂ - y₁) / (x₂ - x₁).
Read full definition →Density
Mass per unit volume, typically in kg/m³ or g/cm³. Different materials have characteristic densities.
Read full definition →Payroll & Benefits (7 terms)
Gross vs. Net Pay
Gross = total earnings before deductions. Net = what actually hits your bank account after taxes and withholdings.
Read full definition →Tax Bracket
A range of income taxed at a specific rate. Higher income does not mean all of it is taxed at the higher rate.
Read full definition →401(k)
A US employer-sponsored retirement plan that lets employees save pre-tax dollars. Often includes employer matching.
Read full definition →Roth IRA
An individual retirement account funded with post-tax dollars; withdrawals in retirement are tax-free.
Read full definition →Social Security
A US federal program providing retirement, disability, and survivor benefits, funded by payroll taxes.
Read full definition →Overtime Pay
Wages paid at a higher rate (typically 1.5×) for hours worked beyond the standard 40-hour workweek.
Read full definition →Severance Pay
Compensation paid by an employer to an employee upon termination, often based on years of service.
Read full definition →Conversions & Units (2 terms)
Metric vs. Imperial
Metric (SI) and Imperial (US customary) are the two main measurement systems. They differ in base units and conversion factors.
Read full definition →Fahrenheit vs. Celsius
Two scales for temperature. Water freezes at 0°C / 32°F and boils at 100°C / 212°F. Conversion: F = C × 9/5 + 32.
Read full definition →All terms: 55 • Last reviewed: June 15, 2026