Normal Modes
Characteristic independent natural patterns of motion in which all parts of an oscillating system move sinusoidally at the same natural frequency.
Governing formula
f_n = n f1 = n v / (2 L)
SI unit
Hz
In depth
Any arbitrary motion of a linear system can be expressed as a linear combination of its fundamental normal modes.
Examples in the real world
Resonant vibrational modes of a drumhead or structural vibration modes of a skyscraper during an earthquake.