GLOSSARY // Market Structure
ETF (Exchange-Traded Fund)
An ETF is a fund that holds a basket of assets and trades on an exchange like a single stock — buy SPY and you own a sliver of all 500 S&P companies with one ticker, tradable any second the market is open.
The machinery that keeps an ETF's price glued to the value of its holdings is creation and redemption. Authorized participants — large trading firms — can swap baskets of the underlying stocks for new ETF shares (or the reverse) whenever the ETF's price drifts from net asset value, arbitraging the gap shut. That mechanism also makes ETFs tax-efficient: redemptions in kind flush out low-basis shares without taxable sales inside the fund.
Costs are the headline advantage. Broad index ETFs charge expense ratios as low as 0.03% a year ($3 per $10,000 invested); SPY, the oldest and most traded US ETF, charges 0.0945%. Niche and leveraged ETFs run 0.5-1%+ and carry structural decay that makes them day-trading vehicles, not holdings.
An investor puts $10,000 into an S&P 500 ETF with a 0.03% expense ratio — $3 a year in fees. The same exposure in a 1.0% fee mutual fund costs $100 a year; compounded at 8% market returns over 30 years, the fee gap alone leaves the ETF holder roughly $24,000 richer on the identical index.
Related terms
Educational only — not financial advice. Definitions simplified for clarity; markets are messier than definitions.