Rules for Writing SI Units
In our day-to-day life we come across number of physical quantities that are to be measured or written. Many people write them incorrectly, here are certain rules to write the SI units:
1) When writing the name of the unit, the first letter of the unit should be in small case and it should be not written in capital case. Thus the unit of length should be written as ‘meter’ and not ‘Meter.’ For example it is correct to write 5 meter and not 5 Meter. Similarly, the unit of mass is written as kilogram and not Kilogram. Some of the units are written after the name of the scientist or other person, even these units should start with small letters. Thus the unit of power should be written as watt and not Watt. Similarly other units are newton, ampere, hertz etc.
2) When writing the symbols for the SI units, if the unit is named after the person, the symbol should start with the capital letter. Thus the symbol for newton is written as N, for ampere it is A, for hertz, it is Hz, for kelvin it is K and so on. If the unit is not the name after the person, its symbol should start with the small letter. Thus symbol for kilogram is kg, for meter it is m, and so on.
3) The symbols for the SI units are written in singular form and not in plural form though they may indicate quantity more than one. Thus five meter of length is written as 5 m and not 5 ms. Similarly it is correct to write 10 kg, but is incorrect to write 10 kgs. If one has to write them in plural forms then full name of the units should be written and not the symbols. Thus it is correct to write 5 meters, 10 kilograms, etc.
4) No full stops or punctuation should be written after the symbols of the SI units. Thus when writing five meters of length it is correct to write 5 m but incorrect to write 5m. or 5m,.