Period
Definition
The time one complete wave cycle — or one full back-and-forth oscillation — takes.
Symbol: · Unit: second (s)
Technical definition
The duration of one oscillation, T = 1/f, measured in seconds. Period is the inverse of frequency: long period means slow oscillation, short period means fast.
Example
A pendulum swinging with a period of 2 seconds completes one full back-and-forth swing every 2 seconds, which means its frequency is 0.5 Hz — one half-cycle per second.
Common confusion
Period is not frequency — they are reciprocals. A 100 Hz tone has a period of 0.01 s, not 100 s. When a problem gives you '0.02 s per cycle,' that number is the period; the frequency is 1 divided by it (50 Hz). Forgetting to invert is the classic slip, especially under exam pressure.