Here's why:

* Frequency is the number of times an event (like a wave cycle) occurs in a given time period. It's usually measured in Hertz (Hz), which represents cycles per second.

* Period is the time it takes for one complete cycle of an event to occur. It's the inverse of frequency, meaning:

Period = 1 / Frequency

Example:

* If a wave has a frequency of 10 Hz (10 cycles per second), its period is 1/10 second (0.1 seconds). This means it takes 0.1 seconds for one complete wave cycle to occur.