25 mins ago, by Sir Cumference
For a function $f$ whose antiderivative is $F$, I always interpreted $\int{f(x) \mathrm{d}x}$ as canceling out the denominator in the antiderivative: $=\int{\frac{\mathrm{d}F}{\mathrm{d}x} \mathrm{d}x}=\int{\mathrm{d}F}$, and then summing up the differentials to get $F$. So, the integral sign is an operator that acts on differentials.