A wave is a disturbance that transfers energy over a distance. It can be seen in various forms like sound waves, water waves, and seismic waves. Waves exhibit periodic motion, which repeats in regular intervals. The amplitude is the maximum displacement from the rest position, while the period (T) is the time for one full cycle. Frequency (f) is the number of cycles occurring in one second, measured in Hertz (Hz). Period and frequency are reciprocals.