The main purpose of the mandatory space is legibility. It is difficult
to read numbers and letters that are jammed together, especially in
complex expressions, just as fiftymeters is harder to read than fifty
meters.
Moreover, whether in symbols or spelled out, the number and unit are
individual factors of the quantity and logically require a space, which
represents multiplication (50 m means 50 [times] meter).
It is true that the prefix is also multiplied by the unit, but no space
is used in that case because they are spelled and pronounced as one word
(inseparable, as the BIPM says).
Furthermore, the widespread American practice has always been to leave a
space, whether the units are SI or non-SI. It's true that ordinary
Europeans generally fail to leave the space (an irritation, when you're
reading European media), but I see no reason to introduce this poor
practice in the U.S., which explicitly violates the long-established
international rules.
I agree that we should explain that a "non-breaking fixed space should
be used whenever there is danger that a quantity may break and wrap to
the next line, or expand in justification." It need not be a thin space.
Dennis Brownridge
-----Original Message-----
From: Bruce Barrow [mailto:[email protected]]
Sent: Thursday, March 12, 2009 08:40
To: [email protected]
Subject: [SI] SI10: space between number and unit symbol
Mr. Bowman:
Further to Jim's comments below:
We are here dealing with an editorial style question. For a time in my
professional career I was a technical editor, an experience that led to
my
discovery of SI nearly fifty years ago. Now I chair the joint IEEE/ASTM
committee that is in the process of revising the SI10 standard.
As you and Jim have noted, you can find a variety of recommendations on
style matters. I think it is entirely unreasonable to permit
"35-millimeter
film" but not "35-mm film". I prefer specifying things that should not
be
touched with a 3-m pole to those that should not be touched with a 10-ft
pole, because I believe in encouraging SI. In other words, I believe
that
the choice of unit is more important than the style question, and I can
tolerate the hyphen..
I know that the Brochure and other standards, including the current
SI10,
require a space between the number and the unit symbol. It is important
to
remember, however, that in fact the number and the unit symbol are
closely
associated, and that association should be preserved. In practice there
is
frequently no space at all, as with 750mL bottles of wine and 10mg
capsules
from the pharmacy, and no space at all seems better to me than use of an
unfettered space. For example, a recent IEEE standard I reviewed had a
line
that looked like -- "at least a 4.7 m separation
is required". To avoid such an appearance I will recommend that we
include in SI10 the restrictions that the space should be "thin, fixed,
and
non-breaking". Thin means about the width of the letter i, fixed means
that
the space does not expand when the line is justified, and non-breaking
means
that the number is not placed at the end of a line with the symbol
appearing
on the next line. I personally would be happy to amend the current
SI10
and make the space optional, but that view may not receive a consensus
in
our committee.
Perhaps you thought you were asking a simple question. Hah!
Bruce Barrow, Chair
Joint IEEE/ASTM Task Force for SI10
----- Original Message -----
From: "James R. Frysinger" <[email protected]>
To: "Lyle Bowman" <[email protected]>
Cc: <[email protected]>; <[email protected]>; <[email protected]>;
<[email protected]>; <[email protected]>; <[email protected]>;
<[email protected]>
Sent: Tuesday, March 10, 2009 5:02 PM
Subject: Re: SI 10 question
Dear Mr. Bowman,
I am the chair of a committee, some members of which represent the
IEEE
portion of the IEEE/ASTM Joint Committee for Maintaining SI 10. Your
message has been forwarded to me for a reply.
Standard practice in the U.S. is to use a space instead of a hyphen
when
unit symbols are used, whether the expression is in noun ("a width of
35
mm") or adjectival form ("35 mm film"). That would comply with the
normative statements of IEEE/ASTM SI 10 as well as NIST SP 811.
Further,
and importantly, it complies with Section 5.3.3 of the SI Brochure
(8th
ed.)
Your suggestion to make an explicit statement in SI 10 regarding
application of this practice to the adjectival form is noted and will
be
considered for the revision (update) now in progress. Thank you for
that
thought!
You may have noticed that SP 811 says the hyphen "is acceptable" (but
not
required) in adjectival forms when the unit name is spelled out
("35-millimeter film"). Personally, I prefer using a space there as
well;
the movement in language is generally toward economy of punctuation,
except as needed to avoid ambiguity.
Thank you very much for your interest in SI 10. Most certainly, we are
pleased to hear that you are working towards improved metrication of
ASTM
standards. If you have any other questions, please do not hesitate to
write or call.
regards,
James R. Frysinger (Jim)
Chair, Standards Coordinating Committee 14
IEEE Standards Association
[email protected] wrote:
Jim,
Please see the communication (below), regarding SI 10.
Thanks,
****************************************************************
David L. Ringle
Manager - IEEE-SA Governance, Policy & Procedures
IEEE Standards Activities Department
445 Hoes Lane Piscataway, NJ 08854-4141
USA
TEL: +1 732 562 3806
FAX: +1 732 875 0524 [email protected]
****************************************************************
March 4, 2009
I'm an ASTM member and have been given the task of revising the
measurement units in many ASTM standards to SI units.
The IEEE/ASTM SI 10-2002 standard has been my primary reference in
doing
this task.
There's one question that I haven't been able to resolve, and that is
whether to place a hyphen between a number and an SI unit when the
combination is used in an adjectival sense. My SI 10 reference
(Section
3.5.1, item d)) says to leave a space between a 'numerical value and
a
unit symbol', and does not comment on the possible adjectival usage.
An earlier ASTM E 380 SI Standard says to hyphenate when the
combination
is used in an adjectival sense, and the current NIST Special
Publication
811 (SP 811) says specifically not to hyphenate in that situation.
Assuming that it's also the intention of the IEEE/ASTM 10-2002
standard
to not hyphenate when a combination of a numerical value and a unit
symbol is used in an adjectival sense, I'd recommend that a specific
statement to that effect be included in the standard.
I'd appreciate being informed if my above assumption is incorrect.
Sincerely,
Lyle Bowman
728 Montecillo Road
San Rafael, CA 96904-3136
Phone: 415-479-3004
Email: [email protected]
--
James R. Frysinger
632 Stony Point Mountain Road
Doyle, TN 38559-3030
(C) 931.212.0267
(H) 931.657.3107
(F) 931.657.3108
