Harmonics
Refers to the frequencies at which a standing wave can be formed on an object.
The natural frequency of an object is often referred to as its harmonics.
By definition every object has an infinite number of possible harmonics. The first harmonic is defined as a frequency equivalent to half a wavelength across the medium of travel. Or simply the Fundamental Frequency. The second harmonic has twice the frequency and one full wavelength (2 waves each half a wave length). and so on.
Note: each subsequent harmonic has a multiple of the fundamental frequency.
Note: The first-harmonic refers to the smallest frequency sufficient to form a standing wave. A wave with half a wave-length reflected back onto itself will produce a two nodes and one anti-node.