Phase

By Brain Lawlor Phase- a particular stage or point of advancement in a cycle; the fractional part of the period through which the time has advanced, measured from some arbitrary origin often expressed as an angle (phase angle), the entire period being taken as 360°.

Phase is a measure of what part of a repetitive cycle any given point in a medium is in. One complete cycle is usually defined a 360 degrees. If a given point in the medium is one quarter of the way through its cycle, its phase is 90 degrees. Relative phase or phase shift is a measure of the difference in phase between two different waves of the same frequency. When the phase shift between two waves is zero, they are at the same point in their cycle at any point in time. They are said to be “in phase” because they line up with each other. When the phase shift between two waves is 180 degrees, they are shifted one half a cycle relative to each other at any point in time. They are said to be “out of phase”. In this case one wave will be going up while the other is going down so to speak.
 * Phase **