Hey all, I just started a fluid mechanics class and I'm having trouble interpreting the physical meaning behind differentials in this free body diagram. For example, γδxδyδz. I know gamma is the specific weight of the block of fluid. And I know δ is the differential length in x, y, or z directions. But together as an expression what does this mean? My thought process is: λ=ρg and it makes sense that the weight of the "block" of fluid is λ*Volume But wouldnt that look something like this: ∫∫∫λδxδyδz If you're not integrating, then what does it mean when they're just hanging there? Also, is there a difference between the notation δx and dx? Thanks!