Which term is used for a waveform with exactly three phases?

• A. Monophasic
• B. Biphasic
• C. Polyphasic
• D. Triphasic

Answer: (D)

A three-phase waveform is described as triphasic. In electrotherapy, how a pulse is built is defined by the number of distinct segments, or phases, it contains. A single-phase pulse is monophasic, a two-phase pulse is biphasic, and when there are three segments in a pulse, we call it triphasic. Triphasic patterns are often designed to balance charge across the pulse, typically by alternating polarities (for example, positive–negative–positive), which helps reduce net DC offset and improves comfort and safety. The term polyphasic, by contrast, refers to any waveform with more than two phases in general, so it doesn’t specify three exactly.