Em dash

[yo4561]

Hi MP,

I know there has been emphasis on not worrying too much about punctuation.

However, I want to clarify my understanding of the em dash. All the Verbal Companion says em dashes are used for the following reasons:
-Can be used as an emphatic comma, semicolon, or colon
-Can also be used to restate or explain an earlier part of the sentence. But unlike the colon, the dash does NOT need to be immediately preceded by the part needing explanation.

From my understanding of the GMAT, GMAC seems to employ the em dash for appositives. So, if my understanding is correct, do the uses above only take place in the form of an appositive (as in what follows the em dash or is offset by em dashes will be an appositive)?

[esledge]

From my understanding of the GMAT, GMAC seems to employ the em dash for appositives. So, if my understanding is correct, do the uses above only take place in the form of an appositive (as in what follows the em dash or is offset by em dashes will be an appositive)?

Appositives can be set off by em dashes, but that's not the only type of structure that you could find offset by em dashes. For example, check out 2021 OG #977 (Heirloom Tomatoes), which has a whole clause between em dashes.

I did a quick look through the OG and found examples of the writers offsetting the following by em dashes:
--a single adverb (for emphasis, I guess)
--appositives
--appositives with long following modifiers
--stand-alone, complete clauses
--"while" and "although" subordinate clauses
(This list is not exhaustive.)

It really can vary a lot! Mostly, em dashes are used for the same reason long modifiers are: to distract you from the rest of the sentence.

My personal approach with em dashes:
--Treat pairs of em dashes as if they are parentheses (typically a "comment" is between them).
--Treat a single em dash as if it is a colon (typically followed by an explanation/example).

Unless the wording within the em dash part is really wrong itself, you can then just ignore the comment/explanation/example and read the remaining sentence.