I generally know how to use a hyphen, but when should I use an en-dash instead of an em-dash, or when should I use a hyphen instead of an em-dash?
An em-dash is typically used to act as a comma or parenthesis to separate out phrases—or even just a word—in a sentence for various reasons (i.e. an appositive). Examples where an em-dash should be used:
An en-dash is used to connect values in a range or that are related. A good rule is to use it when you're expressing a "to" relationship. Examples where an en-dash should be used:
A hyphen is used to join words in a compound construction, or separate syllables of a word, like during a line break, or (self-evidently) a hyphenated name.
Finally, a minus sign is distinct from all three of the above.
If you want to use the correct dash or hyphen in StackExchange comments, just use the appropriate HTML entity:
protected by Jasper Loy Apr 28 '12 at 11:36
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