A sign is an entity which signifies another entity. A natural sign is an entity which bears a causal relation to the signified entity, as thunder is a sign of storm. A conventional sign signifies by agreement, as a full stop signifies the end of a sentence. ( Contrast a symbol which stands for another thing, as flag may be a symbol of a nation).
A symbol is something such as an object, picture, written word, sound or particular mark that represents something else by association, resemblance, or convention. For example, a red octagon may be a symbol for “STOP”.
Percent sign (%) symbolizes 1 per 100 faction of something and is used to indicate the amount of 1 per 100 parts of something.
The symbol of pi (π) is especially known and used in mathematics. In mathematics it symbolizes the value pi that indicates the ratio between it’s circumference and it’s diameter.
Measurement is the process or the result of determining the magnitude of a quantity, such as length or mass, relative to a unit of measurement, such as a meter or a kilogram.
The word measurement stems, via the Middle French term mesure, from Latin mensura and the verb metiri.
We use the International System of Units ( abbreviated as SI from the French language name Systeme International d’Unites) as the modern revision of the metric system. The SI units for the four basic physical quantities : length, time, mass and temperature are :
• Metre (m) = as SI unit of length
• Second (s) = SI unit of time
• Kilogram (kg) = SI unit of mass
• Kelvin (K) n= as SI unit of temperature
We also use some special names for some multiples of some units.
• 100 kilograms = 1 quintal ; 1000 kilogram = 1 metric tonne ;
• 10 years = 1 decade ; 100 years = 1 century ; 1000 years = 1 millenium