LaTeX的标签是我加上去的,此答案为TeX用户准备,非TeX用户慎入。
这几个在符号在TeX中的用法,来自TeXbook:
Book printing differs significantly from ordinary typing with respect to dashes, hyphens, and minus signs. In good math books, these symbols are all different; in fact there usually are at least four different symbols:
a hyphen (-);
an en-dash (–);
an em-dash (—);
a minus sign (-).
Hyphens are used for compound words like ‘daughter-in-law’ and ‘X-rated’. En-dashes are used for number ranges like ‘pages 13–34’, and also in contexts like ‘exercise 1.2.6–52’. Em-dashes are used for punctuation in sentences—they are what we often call simply dashes. And minus signs are used in formulas. A conscientious user of TeX will be careful to distinguish these four usages, and here is how to do it:
for a hyphen, type a hyphen (-);
for an en-dash, type two hyphens (--);
for an em-dash, type three hyphens (---);
for a minus sign, type a hyphen in mathematics mode ($-$).