Stock Market Terminology

Start with the foundation. A stock represents ownership in a company; if you own its stock, you own a slice of the business and a claim on its future profits. A share is a single unit of that stock, so owning 10 shares means you hold 10 of those units. Each stock is identified by a ticker symbol, the short code (AAPL, MSFT, VOO) you type into an app to look it up, because it is faster and less ambiguous than the full company name.

Trades happen on an exchange, a regulated marketplace like the New York Stock Exchange or Nasdaq that matches buyers and sellers and reports prices. An index is a scoreboard, not something you own directly: it tracks the combined performance of a defined group of stocks. The S&P 500 follows roughly 500 large US companies, the Nasdaq-100 leans toward big technology names, and the Dow Jones Industrial Average tracks 30 well-known companies. When the news says the market is up, it usually means one of these indexes rose.

When you place a trade, the order type controls how it fills. A market order buys or sells immediately at the best available price, so it executes fast but the final price can shift a little while it fills. A limit order sets a price boundary: buy only at or below your limit, or sell only at or above it. You get price control in exchange for the risk that the order never fills if the stock does not reach your number.

A stop-loss order is a safety trigger. You set a stop price, and if the stock falls to it, the order activates and sells, capping how much you can lose on a position without watching it constantly. The bid is the highest price buyers are currently willing to pay, and the ask (or offer) is the lowest price sellers will accept. The gap between them is the spread. A narrow spread means a liquid, heavily traded stock; a wide spread signals fewer buyers and sellers, which can make getting a good price harder. Volume, covered below, is closely tied to how tight that spread tends to be.

These are the numbers on a stock's page that hint at what it is worth and how it is priced. Market capitalization, or market cap, is the company's total stock-market value: share price multiplied by shares outstanding. It is how companies get sorted into large cap, mid cap, and small cap. Earnings per share (EPS) is the company's profit divided by its share count, a per-share measure of how much it earns.

The price-to-earnings (P/E) ratio divides the share price by EPS, roughly showing how much you pay for each dollar of profit. A high P/E can mean investors expect fast growth, or that a stock is expensive; a low one can mean a bargain or a struggling business, so it is context, not a verdict. A dividend is a cash payment some companies send shareholders out of profits, usually quarterly. The dividend yield expresses that payment as a percentage of the share price, so a $2 annual dividend on a $100 stock is a 2% yield, making it easy to compare income across stocks of different prices.

These words describe what the market is doing. A bull market is a sustained stretch of rising prices and optimism, while a bear market is a sustained decline, commonly defined as a drop of 20% or more from a recent peak. A milder pullback of about 10% is called a correction, a normal and frequent event rather than a crash. The animal names are just shorthand for direction and mood.

Volatility measures how sharply and quickly prices swing. High volatility means big moves up and down, which is why a volatile stock feels risky even if its long-term direction is fine. Volume is the number of shares traded over a period; high volume means lots of activity and interest, and it often accompanies big price moves and tighter spreads. Together these terms describe the weather of the market: bull or bear for the season, volatility and volume for how stormy any given day is.

Finally, the terms that frame how you actually hold investments. A brokerage account is the account, opened with a broker, that lets you buy and hold securities. Your portfolio is the full collection of what you own across your accounts: every stock, fund, and cash position together. Diversification is spreading that portfolio across many companies, sectors, and asset classes so no single holding can sink the whole thing; our how to build a diversified portfolio guide walks through it in depth.

An ETF (exchange-traded fund) bundles many securities into one holding that trades on an exchange like a single stock, so one purchase can give you hundreds of companies at low cost. A mutual fund is a similar bundle, but it is priced once a day after the market closes rather than trading live, and it is often bought directly from the fund company. Both are ways to own a slice of the whole market without picking individual stocks; our best ETF in every category guide lists the main fund types.

These are the terms that come up first for most people. They are defined here in everyday language so you can read a stock's page or a market headline without reaching for a dictionary every line. Definitions are simplified for clarity; the formal versions can carry extra nuance, and figures like index membership change over time.

A glossary teaches the words, but the terms click fastest when you see them on something you actually own. What is the market cap of the biggest stock in your account? Which of your funds is an ETF versus a mutual fund? How volatile has a given position been against the S&P 500? Those are exactly the questions an AI assistant can answer when it can read your real holdings instead of a generic example.

That is where Walnut fits. It connects your existing brokerage through SnapTrade and lets you ask, in plain language through Claude, ChatGPT, or a built-in assistant, what a term means and how it applies to your own positions, so the vocabulary attaches to real numbers. It is read-only by default, and you approve any trade. Walnut is not an investment adviser; it helps you understand and act on your own portfolio rather than telling you what to buy.

Most of the language reduces to a few groups. A stock is ownership, a share is a unit of it, a ticker names it, an exchange is where it trades, and an index tracks a group of them. Order types control how a trade fills, valuation numbers like market cap and P/E describe what a company is worth and how it is priced, movement words like bull market and volatility describe what prices are doing, and account terms like portfolio and ETF frame how you hold it all.

Once the words make sense, the practical next steps follow naturally: open an individual stock page to see these terms in context, browse an ETF to understand fund bundles, or explore a theme you want exposure to. Definitions here are simplified for learning; confirm specifics on a broker or issuer's site before making any decision.