Basis names the gap between spot and forward prices.
Spot minus forward
Basis is spot minus forward. Here spot is $100.00 and the forward is $105.00, so basis is negative $5.00.
basis=S−F=$100.00−$105.00=−$5.00
Carry language
Because the forward is above spot, this example is contango. If the forward were below spot, that would be backwardation.
F>S⇒contango,F<S⇒backwardation
Market note
Basis language describes a price relationship, not a forecast, fair-value claim, or trading recommendation. Real markets can include storage, funding, margin, liquidity, taxes, collateral, and delivery details. This is descriptive, not investment advice.
basis is descriptive, not a forecast