RussellMc wrote:

>> Isn't the plural Henries? Like Volt -> Volts?
>=20
> If Volts and Amps and Coulombs and Farads and Newtons and ... were
> correct, then Henries might be too, although arguably it would be
> Henrys.
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> But, the "proper" usage, and expect incoming on this, is to not
> pluralise the unit name.
> So 4.56 Volt, 3.2 Farad, 39,000 Ohm etc.

According to most sources it would be 4.65 V or 4.65 volts (not Volt or
Volts) -- in English. (AIUI, the case of the symbols is international,
but the case of the unit names depends on the language. See also below.)

> This
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>      http://en.wikipedia.org/wiki/International_System_of_Units
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> is somewhat quiet on the subject formally (but uses eg "metres" in an
> explanation) but also somewhat different than some other pages on some
> points

Isn't this about the subject matter?

>From the page:

* Names of units start with a lowercase letter (e.g., newton, hertz,
pascal), even when the symbol for the unit begins with a capital letter.
This also applies to 'degrees Celsius', since 'degree' is the unit.

* Names of units are pluralised using the normal English grammar rules;
e.g., "henries" is the plural of "henry". The units lux, hertz, and
siemens are exceptions from this rule: they remain the same in singular
and plural form. Note that this rule applies only to the full names of
units, not to their symbols.

* The official USA spellings for deca, metre, and litre are deka, meter,
and liter, respectively.



> Note that the general advise is that unit names are written in lower
> case (volt, ampere, henry) but that the symbol uses upper case for
> units which are peoples names  (V., A, H, ...).
> The one exception to upper case =3D proper name is L for litre, in some
> administrations only.
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> I have always tended to use eg Watt, Ohm, farad, ... and would be
> inclined to do so unless somebody can make a convincing case for
> "doing things properly".

This is not an attempt to convince you :)

The definitive source for matters SI: <http://www.bipm.org/en/si/>

>From their brochure
<http://www.bipm.org/utils/common/pdf/si_brochure_8_en.pdf>:

"Unit names are normally printed in roman (upright) type, and they are
treated like ordinary nouns. In English, the names of units start with a
lower-case letter (even when the symbol for the unit begins with a
capital letter), except at the beginning of a sentence or in capitalized
material such as a title. In keeping with this rule, the correct
spelling of the name of the unit with the symbol =B0C is =93degree Celsius=
=94
(the unit degree begins with a lower-case d and the modifier Celsius
begins with an upper-case C because it is a proper name)."


I didn't find anything specific about plural vs singular in this
document, but I also didn't search much and one example indicates the
use of plural: "2.6 metres per second". AIUI, this is consistent with
the treatment as ordinary nouns. (As is that in German, for example, it
is "2.6 Meter pro Sekunde" or "4.56 Volt"; ordinary nouns are
capitalized in German.)


For the ones in the USA who think that the Bureau International des
Poids et Mesures is too "international" <g>, its publications are in
alignment with the also very good publications of the NIST:

<http://physics.nist.gov/cuu/Units/index.html>
<http://www.nist.gov/pml/pubs/sp811/index.cfm>

Gerhard

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