Four-by-four (4×4) is a term used to refer to the type of vehicles able to power all its 4 wheels.

If we look more detailed than the first digit shows the total number of wheels (or more accurately the number of axle ends) while the second shows the number of axle ends that are powered. For example 4×2 means a vehicle with four wheels (axle ends) where the torque is sent to two axle ends. Similarly, a 6×4 vehicle has three axles (6 axle ends), where the power is sent to 4 axle ends or two axles.