# Exchange-traded fund (ETF)

Exchange-traded fund (ETF) is an investment fund whose shares trade on a stock exchange, giving investors exposure to a portfolio of assets through a single traded security.

## What it means

An ETF packages a portfolio of assets into shares that investors can trade on an exchange during market hours. Its holdings may include stocks, bonds or other assets, depending on the fund. Some ETFs seek to track an index; others follow a different stated strategy. Owning an ETF share gives you an interest in the fund, not direct ownership of each asset it holds.

An ETF has a market price—the price at which its shares trade—and a net asset value (NAV), which represents the value of its assets minus liabilities per share. The two can differ. A fund’s portfolio also changes over time through price movements, distributions, rebalancing or changes in its strategy.

## How it is calculated

An ETF is a type of fund, not a single metric. Two useful calculations are:

- `Position value (US$) = ETF shares held × market price per share (US$/share)`
- `NAV per share (US$/share) = (fund assets (US$) − fund liabilities (US$)) ÷ ETF shares outstanding`

**ETF shares held** is the number in an investor’s position. **Market price per share** is a quoted trading price, which may change throughout the session. **Fund assets** are the value of the fund’s holdings and other assets; **fund liabilities** are amounts it owes. **ETF shares outstanding** is the number of fund shares used to calculate per-share NAV. Position value uses a market price, while NAV per share uses the fund’s underlying accounting values; neither formula includes an investor’s trading costs.

## Worked example

Suppose a hypothetical ETF holds US$100 million in assets, owes US$1 million and has 1 million shares outstanding. Its NAV per share is `(US$100 million − US$1 million) ÷ 1 million = US$99`.

Now suppose its market quote is US$99.90 bid and US$100.10 ask per share. The bid-ask spread is `US$100.10 − US$99.90 = US$0.20` per share. At the US$100.10 ask, a hypothetical purchase of 10 shares would cost `10 × US$100.10 = US$1,001`, before any commission. At that price, the position is worth US$1,001 by the position-value formula, while the shares’ combined NAV is `10 × US$99 = US$990`.

That US$11 difference does not, by itself, predict a gain or loss: the market quote and NAV are different measures, and both can change. The example is deliberately simplified; an actual ETF’s holdings, pricing and trading costs require separate checks.

## Why it matters before you trade

A single ETF ticker can provide exposure to many holdings, but it does not automatically make a portfolio diversified. Two ETFs may own many of the same stocks, and a narrowly focused ETF may be concentrated in one sector or country. Check the fund’s stated objective, holdings and weighting method when assessing what exposure it adds to a portfolio.

Execution matters too. ETF shares have bid and ask prices, so a spread can affect the cost of entering or exiting a position. Compare the proposed order size with available liquidity, consider the execution conditions, and distinguish a quoted price from the eventual fill price. Ongoing fund expenses and any tracking difference from a stated benchmark are separate from the immediate cost of a trade.

## How PreTrAIde uses it

PreTrAIde is an AI pre-trade analysis platform for stocks. Its described workflow lets users build a basket of one or more stocks with a side, quantity and execution conditions. The product facts do not state that it analyzes ETF holdings, ETF overlap, NAV premiums or discounts, or ETF-specific trading costs.

For an ETF, a pre-trade check can still ask about overlapping holdings, portfolio concentration and the proposed trade’s spread and size. PreTrAIde’s published stock-basket capabilities should not be treated as an ETF analysis or as an investment recommendation.

## Common mistakes

- **Equating an ETF with its index.** A fund may seek to track a benchmark, but its returns can differ because of expenses and other factors.
- **Assuming one ticker means broad diversification.** Holdings and exposures—not the number of tickers—determine concentration.
- **Confusing market price with NAV.** Investors trade ETF shares at market prices, which can differ from NAV.
- **Ignoring the spread.** A small-looking price difference can matter when measured against the size of a trade.

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Source: https://pretraide.com/glossary/etf