There is of course an argument that a symbol could be reserved for the "year" and that the user of the symbol should define which year he means. That would ensure that the symbol is not used for anything else.
-----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Pierre Abbat Sent: 24 August 2007 13:35 To: U.S. Metric Association Subject: [USMA:39275] RE: Energy units On Friday 24 August 2007 03:02, Bill Potts wrote: > There's a problem with y for year. > > The unit y is neither an SI unit nor a unit approved for use with SI. The > largest unit that is approved is d, for day. I've also seen "a" for year, often in "Ma". This conflicts with the are, but I think that the are should be totally gotten rid of. Neither it nor its commonly used multiple, the hectare, agrees with the principle of thousands. If we should have a symbol for the year, which year should it be? There are the tropical year, the sidereal year, and several calendar years. Pierre
