Grammar
Style guide 
Writing about millions and billions
M or m for million?
The International Standard ISO 1000:1992/Amd 1:1998, which Australia adheres to, says millions should be abbreviated to ‘M’.
However, according to the Australian Government style manual, Style Manual: For Authors, Editors and Printers (2002), ‘m’ is preferable to ‘M’ as long as the context is clear. It says: “The use of 'M' to represent 'million' is uncommon in Australia and is not recommended.”
‘M’ or ‘m’? You decide!
Billions
Most writers spell out billion in text ($4 billion). The international abbreviation for billion is 'G', but in practice, I think most writers use ‘bn’ ($4bn).
Billions are tricky as there are different definitions for a billion. The Australian Government style manual says:
"The terms billion, trillion and quadrillion were originally used (as their prefixes suggest) to signify a million multiplied by a factor of two, three and four respectively.
billion = million x million (10 12 )
trillion = million x million x million (10 18)
quadrillion = million x million x million (10 24)
This convention has been overtaken internationally by the alternative approach that was instigated by French mathematicians and then adopted by the United States, whereby:
billion = thousand x million (or 1000 million, or 10 9)
trillion = million x million (10 12)
quadrillion = thousand x million x million (10 15)
Australian and international standards (AS ISO 1000:1998) now acknowledge this as standard usage, affirming what has long been established in financial writing. However, scientists and statisticians usually avoid billion, trillion and quadrillion, preferring to express critical amounts using powers of ten.”
PS My apologies that the numbers representing 'powers of ten' are not in the correct place. I couldn't work out how to do them properly in Dreamweaver.
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