By Ziv Shay | Updated June 2026

Fact-checked for accuracy Reviewed by Ziv Shay Updated June 2026

Sources: IRS, SEC, Federal Reserve, U.S. Bureau of Labor Statistics & U.S. Census Bureau. See our editorial standards.

Investing Glossary

Plain-English definitions of the investing and personal-finance terms that matter most — each with a formula and a worked example.

UPDATED June 2026 — 25 terms and growing

New to investing? Start here. We define 25 of the most-searched investing terms in clear language, with real numbers and links to free calculators so you can put each concept to work immediately.

APY (Annual Percentage Yield)

The real rate of return on savings or an investment over a year, including the effect of compounding.

Asset Allocation

How you divide your portfolio among asset classes like stocks, bonds, and cash to balance risk and return.

Bear Market

A period when stock prices fall 20% or more from recent highs, usually amid pessimism and economic weakness.

Bull Market

A sustained period of rising stock prices, typically defined as a gain of 20% or more from recent lows.

CAGR (Compound Annual Growth Rate)

The smoothed, average yearly growth rate of an investment over a period, assuming profits are reinvested.

Capital Gains

The profit you make when you sell an investment for more than you paid for it.

Compound Interest

Interest calculated on both the original principal and the accumulated interest from prior periods, causing your balance to grow at an accelerating rate.

Cost Basis

The original value of an asset for tax purposes, used to calculate capital gains or losses when you sell.

Diversification

Spreading investments across many assets so that no single loss can sink your portfolio.

Dividend

A portion of a company’s profits paid out to shareholders, usually quarterly, as cash or additional shares.

Dividend Yield

A ratio showing how much a company pays in dividends each year relative to its share price, expressed as a percentage.

Dollar-Cost Averaging

Investing a fixed dollar amount at regular intervals regardless of price, smoothing out market volatility over time.

EPS (Earnings Per Share)

A company’s net profit divided by its number of outstanding shares — the profit attributable to each share.

ETF (Exchange-Traded Fund)

A basket of securities that trades on a stock exchange like a single stock, offering instant diversification at low cost.

Expense Ratio

The annual fee a fund charges, expressed as a percentage of your invested assets.

Index Fund

A fund designed to match the performance of a market index, such as the S&P 500, rather than beat it.

Market Capitalization

The total dollar value of a company’s outstanding shares — share price multiplied by shares outstanding.

Mutual Fund

A pooled investment that collects money from many investors to buy a professionally managed portfolio of stocks or bonds.

NAV (Net Asset Value)

The per-share value of a mutual fund, calculated once daily from the total value of its holdings.

P/E Ratio (Price-to-Earnings)

A valuation metric comparing a company’s share price to its earnings per share, showing how much investors pay per dollar of profit.

Principal

The original sum of money invested or borrowed, before any interest is added.

Roth IRA

A retirement account funded with after-tax dollars, where qualified withdrawals in retirement are completely tax-free.

Simple Interest

Interest calculated only on the original principal amount, never on accumulated interest.

Traditional IRA

A retirement account where contributions may be tax-deductible now, but withdrawals in retirement are taxed as income.

Volatility

A measure of how much an investment’s price swings up and down over time.

→ Ready to start? Read our Index Fund Investing guide

About the AuthorZiv Shay is a software engineer and fintech enthusiast based in Israel, building free financial tools since 2024. Learn more

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