Radioactivity of a substance in which one atom disintegrates per second.

degree Celsius

Division into 100 parts of the difference between the freezing point of water (0°C) and its boiling point (100°C) at standard atmospheric pressure.

pascal

Uniform pressure exerted on a flat surface of 1 m2 with a force of 1 newton.

mole

Quantity of matter equal to the number of atoms in 0.012 kg of carbon 12.

newton

Force required to impart an acceleration of 1 m/s2 to a body having a mass of 1 kg.

kelvin

Zero degrees Kelvin is equal to minus 273.16°C.

kilogram

Mass of a platinum prototype that was accepted as the international reference in 1889; it is stored at the International Bureau of Weights and Measures.

meter

Distance traveled by light in a vacuum in 1/299,792,458 of a second.