Differences between delta W or dW

[dx+dy]

Why in some sites, the work appears like $$\ \ \delta W$$ instead of dW ?

Whats the differences between $$\ \delta W$$ and dW?thanks

 

[HallsofIvy]

$$\delta W$$ refers to a small, but "real" change in W. dW is the differential and actually refers to a limit. The way this is used in physics it really should be $$\delta W$$ but many writers 'bend" the meaning a little and use dW.

 

[pardesi]

in some case $$\delta W$$ refers to work done by force such that it is exact differential