Frequency is generally expressed in which unit?

Frequency is primarily defined as the number of cycles of a periodic wave that occur in a unit of time. The standard unit for measuring frequency is the hertz (Hz), which corresponds to cycles per second. In this context, cycles per second effectively captures the essence of frequency, as it directly relates to how many times a repeating event occurs in one second.

Using cycles per second is essential in various fields, including aviation, where understanding the frequency of systems such as communication and navigation signals is crucial for safe and effective operations. The other options present units that are not appropriate for conveying frequency. Inches and meters measure distance, while cycles per minute (although related) provide frequency information in a less standardized form compared to the universally accepted cycles per second.