The International System of Units (SI) is a standardized system used worldwide for measuring physical quantities. It consists of seven base units, each representing a fundamental dimension of measurement. These base units are the meter (length), kilogram (mass), second (time), ampere (electric current), kelvin (temperature), mole (amount of substance), and candela (luminous intensity). Each SI base unit is defined by specific physical constants or phenomena, ensuring consistency and accuracy in measurements. For example, the meter is defined by the distance light travels in a vacuum in a specific time interval, while the kilogram is based on a physical object known as the International Prototype of the Kilogram.