Basis
The difference between a futures price and the spot price of the same asset.
Basis is the gap between a futures or perpetual price and the spot price of the underlying asset. A positive basis, where the future trades above spot, is called a premium or contango. A negative basis is called a discount or backwardation. For a dated future, the basis narrows toward zero as the contract approaches expiry.
On our site, basis is shown in dollars and as a percentage of spot. Use the percentage to compare markets with different price levels.
Traders care because basis reflects financing costs, demand for leverage and sentiment. A wide basis on a dated contract can be captured by buying spot and selling the future, after the costs of doing so.
Worked example (illustrative numbers, not real data): spot is 2,000 and the three-month future is 2,030. The basis is 30 points, or 1.5 percent. If the future converges to spot at expiry, the 30-point gap closes.