Real world examples

I found this definition in The Elements of Typographic Style by Robert Bringhurst, it says, "The en is a connecting dash; it represents a span of time or space. The em is a separating dash—to set apart a thought or idea."

Dashes are not commas or parenthesis , they are not interchangeable.

Crabs have 5 pairs of walking legs - the first set is also for defense. This is totally incorrect, a semi-colon would have worked just fine. I think that they chose to use a dash because a lot of comma's had already been used and the second half is a completely different sentence an afterthought to the first half. The two stand alone perfectly fine, so they should be written that way.

1. By overcoming the seven devils that ruin success (false success, fear of change, guilt, vanity, impatience, habit, and the clock) author James Dillehay turned his life on a new path.

2. James Dillehay’s father had painstakingly built the business, an accomplishment that reflected a steady vision of success.

3. The work of Sufi Master Adnan Sarhan, director of the Sufi Foundation of America, develops higher intelligence and awareness through a wide range of techniques; exercises, meditation, drumming, movement, dancing, and whirling that heighten concentration.

4. Conflicting desires; one for financial security, the other to study with Adnan, often waged war in Dillehay’s troubled brain.

5. Dillehay chose to follow the path of the Sufi, the path that offered no promises, the path that would force Dillehay to be the maker of his own destiny.

6. Dillehay claims that the second devil (fear of change) can be overcome only when someone’s desire to change is stronger than the desire to stay stuck.

7. Impatience, rushing to complete an activity before its natural time, creates stress which in turn creates more impatience.

8. Sometimes we get so wrapped up in something (our job, our family, a relationship) that we forget about ourselves.

9. After the first day of the workshop, (December 4, 1994) the participants cleared their thoughts and felt a sense of readiness.

The en is a connecting dash; it represents a span of time or space. The em is a separating dash—to set apart a thought or idea.