Punctuation

Typists have a convention whereby a single space is left after a mid-sentence comma, and two spaces are left after a sentence-ending period. How do we enforce this if LATEX treats a string of spaces just like a single one? The answer, unsurprisingly, is that we don't.

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To have a comma followed by the appropriate space,  we simply
type a comma follows by at least one space. To end a sentence
we type a period with at least one following space.     No space will
be inserted if we type a comma or period followed straight away
by something other than a space, because there are times when
we won't require any space, i.e., we do what comes narurally.
will produce

0.10.8To have a comma followed by the appropriate space, we simply type a comma follows by at least one space. To end a sentence we type a period with at least one following space. No space will be inserted if we type a comma or period followed straight away by something other than a space, because there are times when we won't require any space, i.e., we do what comes naturally.

LATEX will produce suitable space after commas, periods, semi-colons and colons, exclamation marks, question marks etc. if they are followed by a space. In stretching a line to justify to the right margin, it also knows that space after a punctuation character should be more ``stretchable'' than normal inter-word space and that space after a sentence-ending period should be stretched more than space after a mid-sentence comma. TEX knows the nature of punctuation if you stick to the simple rules outlined here. As we've already said, those rules tell LATEX how to distinguish consecutive words, sentences, phrases, etc.

Actually, there is more to ending sentences than mentioned above. Since LATEX cannot speak English, it works on the assumption that a period followed by a space ends a sentence unless the period follows a capital letter. This works most of the time, but can fail. To get a normal inter-word space after a period that doesn't end a sentence, follow the period by a control space—a \ (a \ character followed by a space or return). Very rarely, you will have to force a sentence to end after a period that follows a capital letter (remember that LATEX assumes this doesn't end a sentence). This is done by preceding the period with a \@ command (you can guess from the odd syntax that this is rarely needed).

It's time we saw some examples of this. After all, this is our first experience of control symbols (don't worry, there are many more to come).

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We must be careful not to confuse intra-sentence periods
with periods that end a sentence, i.e.\ we must remember
that our task is to describe the sentence structure.  Periods
that the typesetter requires a little help with typically result
from abbreviations, as in etc.\ and  others.  We have to work
somewhat harder to break a sentence after a capital letter,
but that shouldn't bother us to much if we keep up our intake
of vitamin E\@.  All this goes for other sentence-ending
punctuation characters, so I could have said vitamin E\@!
Fortunately, these are rare occurrences.
results in

0.10.8We must be careful not to confuse intra-sentence periods with periods that end a sentence, i.e. we must remember that our task is to describe the sentence structure. Periods that the typesetter requires a little help with typically result from abbreviations, as in etc. and others. We have to work somewhat harder to break a sentence after a capital letter, but that shouldn't bother us to much if we keep up our intake of vitamin E. All this goes for other sentence-ending punctuation characters, so I could have said vitamin E! Fortunately, these are rare occurrences.

Quotation marks is another area where LATEX will do some work for us. Keyboards have the characters `, `, and " but we want to to have access to each of `, ', ``, and ''. So we proceed like this:

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`\LaTeX' is no conventional word-processor, and
to to get quotes, like ``this'', we type repeated
` and ' characters.  Note that modern
convention is that ``punctuation comes after
the closing quote character''.
which gives just what we want

0.10.8`LATEX' is no conventional word-processor, and to to get quotes, like ``this'', we type repeated ` and ' characters. Note that modern convention is that ``punctuation comes after the closing quote character''.

Very rarely, you have three quote characters together. Merely typing those three quote characters one-after-the-other is ambiguous—how should they be grouped? You tell LATEX how you want them grouped by inserting a very small space called \,.

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``\,`Green ham' or `Eggs?'\,'' is the question.
gives the desired result

0.10.8`` `Green ham' or `Eggs?' '' is the question.

Since we have a typesetter at our disposal, we might as well use the correct dashes where we need them. There are three types of dash: the hyphen, the endash, and the emdash. A minus sign is not a dash.

Hyphens are typed as you'd hope, just by typing a - at the point in the word that you want a hyphen. Don't forget that LATEX takes care of hyphenation that is required to produce pretty linebreaks. You only type a hyphen when you explicitly want one to appear, as in a combination like ``inter-college''.

An endash is the correct dash to use in indicating number ranges, as in ``questions 1–3''. To specify an endash you type two consecutive dashes on the keyboard, as in 1--3.

An emdash is a punctuation dash, used at the end of a sentence—I tend to use them too much. To specify an emdash you type three consecutive dashes on the keyboard, as in ``...a sentence---I tend to...''.

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Theorems 1--3 concern the semi-completeness
of our new construct---in the case that it
satisfies the first axiom.
yields

0.10.8Theorems 1–3 concern the semi-completeness of our new construct—in the case that it satisfies the first axiom.