Diffraction vs. Interference

The terms diffraction and interference a often used loosely, inconsistently, and sometimes even interchangeably.  Some of the usages are just contextual and historical.  If there is a difference, these sites attempt to explain it.

http://www.differencebetween.com/difference-between-diffraction-and-vs-interference/ Links to an external site.

http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/mulslid.html Links to an external site.

http://srk4you.expertscolumn.com/article/interference-vs-diffraction Links to an external site.

http://web.utk.edu/~cnattras/Phys250Fall2012/modules/module%201/diffraction_and_interference.htm Links to an external site.

https://www.physicsforums.com/threads/diffraction-vs-interference.327504/ Links to an external site.

http://dev.physicslab.org/Document.aspx?doctype=3&filename=PhysicalOptics_InterferenceDiffraction.xml Links to an external site.

http://intro.phys.psu.edu/class/251Labs/10_Interference_&_Diffraction/Single_and_Double-Slit_Interference.pdf Links to an external site.  (figure 6)

Links to an external site.