Help please!!! Diffraction and interference?

so I understand how an interference pattern pattern is produced by two slit interference and diffraction grating and how their patterns are produced. However I fail to understand how in a single slit diffraction can interference occur to produce the pattern with a big central fringe. I mean the pattern can only be produced if interference occurs but i can can't see any interferencee of waves in a single slit diffraction so how is the pattern produced??? help please ..i m stuck