I am very confused about the physical meaning of the concept "flux" I am really trying to understand what it means, what unit it has, but I keep reading contradicting definitions. So, on the one hand, I read that "...flux is defined as the rate of flow of a property per unit area, which has the dimensions [quantity]·[time]−1·[area]−1" (this is from the Wiki article). So basically it is: Whatever-Quantity/Unit-Area But then I keep reading and I see that it's actually the surface integral of a vector field. So now we are multiplying the quantity by unit area! So which one is it, are we dividing or multiplying? Then there is also the notion of flux density... Which is flux per unit area. Well, if the first definition is true, then this becomes [quantity]·[area]−1·[area]−1 or [quantity]·[area]−2. If it's the second definition it becomes [quantity]·[area]−1·[area] or just [quantity]? Please somebody help me sort the mess that's in my head (or potentially in the terminology itself).