An individual mode is a particular frequency and phase (direction) of vibration. Spectral vibration is were you take a particular vibration time-wave form and view its individual frequency components...
a regular periodic variation in value about a mean a vibration is a movement up and down or side to side
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The word vibration can be defined as the act of vibrating or the condition of being vibrated. It is a very rapid movement or motion. It can also be called a quiver.