This document discusses measurement, physical quantities, dimensions, and dimensional analysis. It defines fundamental and derived physical quantities. Dimension is defined as how physical quantities relate to fundamental quantities of mass, length, and time. Dimensional analysis shows how physical quantities relate to each other and can be used to derive formulas, check the homogeneity of equations, and convert between units. Errors are deviations between measured and exact values. Dimensional analysis has limitations and cannot be used for trigonometric, logarithmic, or exponential formulas or detect dimensionless constants.