what?deformation?strain?

Monday morning sink in the deformation and strain differencs.
caught in a box, after i read the lecturernotes.

http://www.engin.umich.edu/class/bme456/ch4alternatestress/bme332altstress.htm
file:///C:/Users/fruitkiwi/Desktop/BME%20332%20%20Alternate%20Definitions%20of%20Stress.htm
http://www.engin.umich.edu/class/bme456/ch3strain/bme456straindef.htm

http://www.math.nyu.edu/faculty/tabak/vorticity.pdf