Phthalates are another class of chemicals that are often used in deodorants and antiperspirants that you may want to avoid. Phthalates are used in cosmetics, synthetic fragrances, plastics, body care products and medical goods. They help to dissolve other ingredients and to create a better consistency.
A harmonic is a signal or wave whose frequency is an integral (whole-number) multiple of the frequency of some reference signal or wave. The term can also refer to the ratio of the frequency of such a signal or wave to the frequency of the reference signal or wave.
Simple harmonic motion is any motion where a restoring force is applied that is proportional to the displacement and in the opposite direction of that displacement.