Why strain has no unit?

What is Poisson’s ratio? Why does it have no unit?

What is Poisson’s ratio? Why does it have no unit?

Which one among, strees and strain is more fundamental and why?

Acceleration has the unit (in SI system) ms^(-2) . It is a base unit?

Recall the experiment done by Frederick Griffith. If RNA, instead of DNA was the genetic material, would the heat killed strain of strep have transformed the R-strain into virulent strain? Explain your answer.

Why liquid has no definite shape?

Which quantity has the unit of m//s^(2) ?