Basis
The difference between a futures contract's price and the current spot price of the same asset.
Basis is usually quoted either as a percentage of spot or annualized to make contracts of different lengths comparable. It reflects the cost and demand for holding leveraged exposure through the futures market, and it must converge to zero at expiry because the contract settles against the spot index. Traders capture it with a cash-and-carry position, acquiring the asset while selling the future, which locks the gap but ties up capital on two venues and carries exchange, margin, and custody risk for the full period. Note that in physical commodity markets the word usually means local cash price minus futures; in digital assets it conventionally means futures minus spot.
En pratique
A three-month contract trading above spot implies an annualized basis that traders compare against the cost of funding the position.
Le malentendu courant
Basis is not a yield paid by anyone; realizing it requires both legs to be maintained until expiry, with all the venue and collateral risk that entails.