An important point: SI metric unit short forms are officially designated at
symbols, not abbreviations.
This seemingly minor point is importent because it relates to several other
usage rules:
SI symbols are never followed by a period (whereas abbreviations are).
SI symbols are never followed by an "s" to form a plural (although
abbreviations sometimes are).
SI symbols are always of the specified case (capital or lower case), so
that (for example)
the symbol for kilowatts is kW. The forms "KW", "kw" and "Kw" are all
incorrect.
SI symbols are the same regardless of language or alphabet. The symbol for
ohms, for example,
is the Greek letter capital omega (Ω) regardless of whether a
document is written in
English or Greek or Swahili or Japanese, etc.
All these special characteristics of the SI short forms are emphasized by
designating them as
symbols, not abbreviations.
That is why some of your expressions (below) are incorrect.
On Jun 2 , at 1:55 PM, Paul Rittman wrote:
> You can see what I have, on this pdf: http://www.paulrittman.com/Metric.pdf
> Area...
> Los Angeles County is 10,577 square km
>
The expression "square km" is a mixture of a word (square) and a symbol (km).
Correct form is to use all words (square kilometre) or all symbols (km²). *
> California is some 425,000 square km (423,970 km2)
>
"square km" is wrong as noted above. "km2" is wrong because the 2 should be an
exponent;
however, see footnote in PS below *. This "error" may be an equipment error not
a human error.
However, it is still an error.
> Alaska has some 1.7 million square km (1,717,854 km2)
>
Same two errors
> The United States is some 10 million square km (9,826,675 sq km) Russia is 17
> million sq km (17,098,242 sq km)
>
One error the same as earlier, but new one appears.
The expression "sq km" is wrong because it combines an abbreviation (sq) and a
symbol (km).
Use all words (square kilometre) or all symbols (km²). Never use abbreviations
at all.
Regards,
Bill Hooper
=====================
* PS
The superscript "2" for square does not always show properly on different
computers.
This should be the correct version of the symbol for square kilometres:
km²
If this does not show as "km" followed by the exponent "2", then your equipment
is not reading my message correctly.
