phase constant

is: the value of the phase when (also known as the initial phase). [P5.1, P5.4, P5.5]

is exemplified: by the constant that appears in the general solution of the SHM equation when that solution is written in the form [M6.3, P5.5]

is also exemplified: by the constant that appears in the equation describing a sinusoidal wave when the equation is written in the form [P5.6]

conventionally is quoted: in the range [P5.1]

is: a number, not an angle, though it may be given an angular interpretation. [M1.6, M6.3, M6.4]