# What's the meaning of a $d$ with a stroke when using Leibniz notation?

I'm studying engineering and there's a physics teacher that strikethroughs the derivative $$d$$ when writing an expression for power (which is work over time). I know physics teachers are known to abuse mathematical notation, but this intrigued me as I had never seen it used and couldn't find anything online. So the expression she writes is:

$$đW/dt = ...$$

What does it mean for the $$d$$ to be struck like this?

I've seen this frequently in physical chemistry books. It's to remind you that this is an inexact differential that results in a path-dependent integral. So, for example, it would be used with $$dq$$ or $$dw$$, but not with $$dE$$ or $$dS$$. They call $$E$$ and $$S$$ state variables, but $$q$$ and $$w$$ are really not well-defined functions — they depend on the path/process, not just on the endpoints.
• Thank you for your answer. So does this notation have any use outside of physics/chemistry? Also, I assume $q$ refers to heat right? – Carlos Gruss Aug 13 at 20:15
• I don't know other places. In math we will write $d\theta$ even though the polar coordinate is not globally defined; but here at least the differential is locally exact and independent of any choices. – Ted Shifrin Aug 13 at 20:18
• I think the $\delta$ ($\delta Q$ and $\delta W$) is more common in physics (personally, I didn't see that kind of d before). – Botond Aug 13 at 21:11