In general physics, delta-v is a change in velocity. The Greek uppercase letter Δ (delta) is the standard mathematical symbol to represent change in some quantity.

Depending on the situation, delta-v can be either a spatial vector (Δv) or a scalar (Δv). In either case it is equal to the acceleration (vector or scalar) integrated over time:

• Vector version:
  $${\displaystyle \Delta \mathbf {v} =\mathbf {v} _{1}-\mathbf {v} _{0}=\int _{t_{0}}^{t_{1}}\mathbf {a} \,dt}$$

  
• Scalar version:
  $${\displaystyle \Delta v={v}_{1}-{v}_{0}=\int _{t_{0}}^{t_{1}}a\,dt}$$

  

If acceleration is constant, the change in velocity can thus be expressed as: ${\displaystyle \Delta \mathbf {v} =\mathbf {v} _{1}-\mathbf {v} _{0}=\mathbf {a} \times \Delta t=\mathbf {a} \times (t_{1}-t_{0})}$ where:

• v₀ or v₀ is initial velocity (at time t₀),
• v₁ or v₁ is subsequent velocity (at time t₁).

Change in velocity is useful in many cases, such as determining the change in momentum (impulse), where: ${\displaystyle \Delta \mathbf {p} =m\Delta \mathbf {v} }$, where ${\displaystyle \mathbf {p} }$ is momentum and m is mass.