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" Numbers
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Chapter 3. Punctuation
Correct There were 88,000 data points, 2500 of which had to be
discarded.
Preferred There were 88 000 data points, 2500 of which had to be
discarded.
3.5.4. Use With Other Marks
Commas are used with other marks of punctuation as follows:
" Commas precede closing quotation marks.
" Commas follow a closing parenthesis if the comma would appear without the parenthetical matter.
" Commas rarely precede an open parenthesis, only if the parenthetical matter clearly limits the following word
(see section 3.10).
" Other marks of punctuation--semicolon, colon, dash, period--supercede and replace the comma; thus, the
"partner" of an enclosing comma may be another mark of punctuation.
3.6. Em Dash
Like the comma, the em dash2 is used both to enclose and to separate, and like the comma, an enclosing dash
needs a partner.
In fact, enclosing dashes are replacements for enclosing commas in order to add emphasis. Ebbitt and Ebbitt
(1982) suggest a useful philosophy toward using the dash:
If used sparingly, the dash suggests a definite tone, often a note of surprise or an emphasis equivalent to a mild
exclamation. If used regularly in place of commas, colons, and semicolons, it loses all its distinctiveness and
becomes a sloppy substitute for conventional punctuation. At its best the dash is a lively, emphatic mark.
3.6.1. Dashes That Enclose
Dashes may replace commas in enclosing interrupting elements and non-restrictive modifiers and appositives (see
section 3.5.2).
" Dashes are appropriate when a comma might be misread, for example, as a serial comma:
Wrong The lasant gas, argon, and 3He were allowed to mix for 45
minutes.
2
In typeset material, there are two dashes: the em dash, which is the width of the letter M, and the en dash,
which is half as wide. In typewritten material, the em dash is represented by two hyphens with no space around
them, and an en dash is represented by a hyphen. Here the em dash will be referred to as simply "dash."
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Chapter 3. Punctuation
The lasant gas--argon--and 3He were allowed to mix for 45
Better
minutes.
" Dashes are also appropriate when the enclosed element contains internal commas:
Of the lasant gases studied--argon, xenon, krypton, and neon--argon offers the most promise.
The most promising lasant gas--argon, which is the lightest gas studied--produced laser output
power of 4 W.
" Use dashes when the enclosed element needs emphasis.
" Enclose by dashes a complete sentence that interrupts another:
Wrong The one-sided spectrum, engineers call it simply
"spectrum," is the output of most spectral analyzers.
Correct The one-sided spectrum--engineers call it simply
"spectrum"--is the output of most spectral analyzers.
Commas are insufficient to enclose an interrupting sentence; dashes or parentheses are required.
The choice of commas, dashes, or parentheses to enclose a nonrestrictive or interrupting element depends on the
relation of the element to the rest of the sentence and on the emphasis it requires ( Effective Revenue Writing 1,
IRS 1962):
" Commas (most frequently used) indicate only a slight separation in thought from the rest of the sentence.
" Dashes emphasize the element enclosed and clarify meaning when the element contains internal commas.
" Parentheses indicate that the enclosed element is only loosely connected to the rest of the sentence and therefore
tend to de-emphasize it.
3.6.2. Dashes That Separate
The dash is used to separate sentence elements in essentially three situations:
" A dash separates a group of antecedents from their pronoun that is the subject of the sentence:
Argon, xenon, krypton, and neon--these are the possible choices of noble gases for use in nuclear
pumped lasers.
" In a displayed list, a dash may separate the item from an explanatory statement:
Support systems for the facility supply the following:
1. Air--The 600-psi system can deliver a flow rate of 300 lb/sec for 3 min.
2. Cooling water--The closed-loop system delivers 450 gal/min at 550 psig.
3. Gaseous propellants--Hydrogen, oxygen, and nitrogen are supplied from tanks at 2400 psia.
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Chapter 3. Punctuation
" A dash may separate two clauses when the second amplifies or restates the first:
The toughness of pseudo-maraging steel degrades at cryogenic temperatures--at -320 deg F, its
Charpy impact energy is 6 ft-lb.
The colon (section 3.4.1) or semicolon (3.15.1)may also be used for this purpose. The dash is less formal than
the colon and more emphatic than the semicolon.
" A dash may precede a phrase like that is, namely, and for example when it introduces a summarizing or
explanatory phrase or clause at the end of a sentence, but a comma or semicolon may also be used (Rowland
1962). If an explanatory clause follows the sentence, a semicolon is necessary; if an explanatory phrase follows,
a comma is sufficient. If the explanatory phrase or clause receives enough emphasis by being at the end of the
sentence, use a comma or semicolon, whichever is appropriate:
Moderate emphasis Other random processes have average properties that vary appreciably with time,
for example, the load demand on an electric power generating system.
Some random processes are reasonably independent of the precise time; that is,
measurements made at different times are similar in their average properties.
A dash would further emphasize the explanatory material:
Emphatic Other random processes have average properties that vary appreciably with time-- [ Pobierz całość w formacie PDF ]