Analogous to impulse, the angular impulse is the integral of torque (single-axis) over the time it acts. Very often the term is used for applications of torque over very short times, in which case it simply reduces to the product of the torque τ with the time interval Δt.
As with many of the equations dealing with rotational motion, care must be exercised in the use of this definition. we are here assuming single-axis torque, acting along a single well-defined direction.