Rules for writing SI Units
1. Symbols for units are written without capital letters, except when it is derived from name. Example: "t" for time "h" for hour "m" for meter 2. Symbols for units derived from proper name are written in capital. Example: "A" for ampere "W" for watt 3.Full names of units are written with lower case letters only. Example: newton henry 4. A space is left between symbols of compound units. Example: N m 5. A space is left between the number and symbol. Example: 56 J 5 A 6. Only one SI prefix is permitted. Example: kA MJ 7. A symbol should not be followed by a fullstop except when it is a product. Example: kg.m 8. Numerals with more than three digits shall be written without commas and with a narrow spacing at an interval of three digits. Example: 45 006 72 674 9. A number with four figures is not broken as mentioned above. Example: 4321 10. A symbol of a unit is placed after the decimal