Volume

Volume answers the question: how much trading actually happened? For stocks, it is typically counted in shares. For futures, it is counted in contracts. For currencies, it is usually counted in notional value (the total dollar amount traded). For cryptocurrencies, exchanges report both coin volume and its dollar equivalent. Because the unit varies so much by market, comparing volume across asset classes requires care — see commodity units and contracts for how this plays out in raw materials markets.

Volume appears alongside price on nearly every price chart because analysts have long used it to assess the conviction behind a price move. The folk wisdom is that a price rise on high volume suggests broad participation and may be more durable, while a price rise on thin volume might reflect a small number of trades in a quiet market. This is sometimes called "volume confirmation." However, it is a pattern traders observe and debate — not a rule with guaranteed outcomes.

Suppose a hypothetical stock rises 3% on a day when only 100,000 shares trade, versus a day when 5 million shares trade. The same percentage gain looks different through a volume lens: one happened in a nearly empty market, the other with heavy participation. Neither tells you with certainty what comes next, but analysts read the context differently.

Volume also matters for liquidity assessment. Consistently high volume generally means tighter bid-ask spreads and less slippage, because many participants are competing to trade. Thin volume environments — common in holiday-shortened sessions (check market holidays) or in niche asset classes — are where liquidity stress tends to surface first.