Periodic changes are those that repeat every certain period of time. This is a topic that fascinates me greatly. For example, midnight is a periodic phenomenon. Two consecutive midnights mark the length of a day. Periodic phenomena can be temporal and wave-like. I will first refer to temporal phenomena and then to wave-like phenomena. Periodic publications are those that appear every certain period of time. They can be daily, weekly, or monthly. The year is another periodic phenomenon. In clocks, we have artificial periodic phenomena: the second, the minute, and the hour. Other artificial periodic phenomena are the week, the month, the decade, etc.
The stars in the universe are governed by periodic phenomena. An example is Halley Comet, which passes close to the Sun every 75 years.
According to their speed, periodic phenomena are classified as fast and slow. Temporal phenomena are slow. Waves are fast periodic phenomena. Waves are characterized by frequency, period, wavelength, and speed. Light and sound are waves.
Elvis Sibilia, Florida, Estados Unidos