The displacement of a particle in SHM is in opposite phase with:

 $$\begin{gathered} \mathrm{For} \mathrm{a} \mathrm{simple} \mathrm{harmonic} \mathrm{oscillator} \\ \mathrm{displacement}=\mathrm{y}=\mathrm{Asin\omega t}, \\ \mathrm{acceleration}=\mathrm{a}=-{\mathrm{A\omega }}^2\mathrm{sin\omega t} \\ B\mathrm{ecause} \mathrm{of} \mathrm{negative} \mathrm{sign} \mathrm{the} \mathrm{phase} \mathrm{difference} \mathrm{between} \\ \mathrm{above} \mathrm{two} \mathrm{equations} \mathrm{is\pi }, \mathrm{that} \mathrm{is} \mathrm{opposite} \mathrm{in} \mathrm{phase}. \end{gathered}$$