Fundamental Quantities: Physical quantities that are independent of other quantities and cannot be resolved further, consisting of length (metre, m), mass (kilogram, kg), time (second, s), electric current (ampere, A), thermodynamic temperature (kelvin, K), luminous intensity (candela, cd), and amount of substance (mole, mol).
Derived Quantities: Physical quantities expressed as products or quotients of fundamental quantities, such as area ($m^2$), volume ($m^3$), density ($kg/m^3$), velocity ($m/s$), acceleration ($m/s^2$), and force ($kg\cdot m/s^2$ or Newton).
SI System of Units: The internationally accepted coherent system of units established in 1960, featuring seven base units and two supplementary units: plane angle (radian, rad) and solid angle (steradian, sr).
Simple Machines: Mechanical devices that alter the magnitude or direction of an applied force to make work easier, operating on the principle of conservation of energy without changing the total work done.