List the conventions followed while using SI units.

Following conventions should be followed while writing S.I. units of physical quantities:

1. Unit of every physical quantity should be represented by its symbol.

2. Full name of a unit always starts with smaller letter even if it is named after a person, eg.: 1 newton, 1 joule, etc. But symbol for unit named after a person should be in capital letter, eg.: N after scientist Newton, J after scientist Joule, etc.

3. Symbols for units do not take plural form.

4. Symbols for units do not contain any full stops at the end of recommended letter.

5. The units of physical quantities in numerator and denominator should be written as one ratio. For example the SI unit of acceleration is m/s² or m s^-2 but not m/s/s.

6. Use of combination of units and symbols for units is avoided when physical quantity is expressed by combination of two. For example, The unit J/kg K is correct while joule/kg K is not correct.

7. A prefix symbol is used before the symbol of the unit.

• a. Prefix symbol and symbol of unit constitute a new symbol for the unit which can be raised to a positive or negative power of 10.

For example,

1 ms = 1 millisecond = 10^-3 s

1 μs = 1 microsecond = 10^-6 s

1 ns = 1 nanosecond = 10^-9 s

• b. Use of double prefixes is avoided when single prefix is available.

10^-6 s = 1 μs and not 1 mms

10^-9 s = 1 ns and not 1 mμs

8. Space or hyphen must be introduced while indicating multiplication of two units e.g., m/s should be written as m s^-1 or m-s^-1.