Delta-v is defined as:

Delta-v is defined as:

• A. The velocity change required to perform a maneuver.
• B. The total velocity of the spacecraft in orbit.
• C. The drag force acting on the spacecraft.
• D. The velocity at which orbital energy is maximized.

Answer: (B)

Delta-v represents the velocity change required to perform a maneuver. It measures how much speed (and possibly direction) you must impart to the spacecraft to transition from its current trajectory to the desired one. In practice, delta-v is the difference between the spacecraft’s velocity before a burn and after the burn, i.e., the impulse needed to alter your path.

It is not the spacecraft’s current speed in orbit, which depends on where you are in the orbit and the orbit’s size and shape. It is not a drag force, which is a resisting force acting on the vehicle. And it isn’t a particular velocity at which orbital energy is maximized—orbital energy changes with mission goals, but delta-v is about the required change in velocity, not a specific velocity value.

So the concept described as the velocity change required to perform a maneuver best matches what delta-v actually measures.