Light scattering by droplets, particles or highly organised obstacles like diffraction gratings is sometimes referred to as diffraction and sometimes as interference. Which is it?

Francesco Grimaldi first used 'diffractio' in the 1600s to describe 'the deviation of light from propagation in a straight line'. Thomas Young introduced the 'Principle of Interference' in the early 1800s in his new wave theory of light.

There is no significant physical distinction between the two terms.   

Diffraction can be used to label the overall process where light waves propagate outwards in many directions having encountered an obstacle that scatters the original coherent illumination. Some of these waves are superposed and where the wave crests reinforce there is brightness, where they are of opposite magnitude they cancel and there is darkness. This is 'interference' but the distinction between the two is really mostly terminological rather than physical.