Thenatural frequency represents an angular frequency, expressed in radians per second. The damping ratio is a dimensionless quantity.
In this situation, the system will oscillate at the natural damped frequency \omega_\mathrm , which is a function of the natural frequency and the damping ratio.
Source: Wikipedia > Damping
What is QuickyWiki? QuickyWiki blends the depth of Wikipedia with the ease and speed of Cliffs Notes.