In the equation
y(x, t) = a sin (kx + t + )
the term with distance travelled 'x' is called angular wave number or propagation constant
Hence k is the angular wave number.
In the equation
y(x, t) = a sin (kx + t + )
the term with time 't' is called angular angular velocity or angular frequency
Hence is the angular frequency.
In the equation
y(x, t) = a sin (kx + t + )
The term represents initial phase or epoch
Hence the term is initial phase