Measurand, error, uncertainty কী?

Example 1.19 (The density of a cylinder)

A cylinder: $m = 47.32\,\mathrm{g}$ ($u = 0.01\,\mathrm{g}$), $d = 12.00\,\mathrm{mm}$ ($u = 0.02\,\mathrm{mm}$), $h = 50.2\,\mathrm{mm}$ ($u = 0.1\,\mathrm{mm}$). $\rho = 4m/(\pi d^2 h)$, so the relative uncertainty squared adds $(0.01/47.32)^2 = 4.5 \times 10^{-8}$, $(2 \times 0.02/12.00)^2 = 1.1 \times 10^{-5}$ and $(0.1/50.2)^2 = 4.0 \times 10^{-6}$: the diameter dominates, because it is squared and measured to $0.17\%$. $u(\rho)/\rho = \sqrt{1.5 \times 10^{-5}} = 0.39\%$; $\rho = 8334\,\mathrm{kg}/\mathrm{m}^{3}$, so $u(\rho) = 33\,\mathrm{kg}/\mathrm{m}^{3}$: $\rho = (8.33 \pm 0.03)\times10^3\ \mathrm{kg}/\mathrm{m}^{3}$ — brass.