As noted in SBLHS 2 §188.8.131.52, authors should distinguish between hyphens (-), en dashes (–), and em dashes (—). The CMS FAQ on the topic explains the differences between the three as follows: a hyphen connects “two things that are intimately connected”; an en dash connects “things that are related to each other by distance”; an em dash is used to indicate an “additional thought” or as “substitute for something missing.” In practical terms, the distinctions are as follows:
1. Hyphens are used to separate compound words and numbers (CMS §§6.76–77).
For rules concerning the use of hyphens with compound words, see SBLHS §184.108.40.206 and, in more detail, CMS §§7.77–85.
2. En dashes are used to indicate ranges, especially those in dates, verses, and pages (CMS §§6.78–80).
As CMS §6.78 states, the en dash should never be used if the word from or between precedes the first element of a pair. Instead, use to or and:
from 1990 to 1991
between 1990 and 1991
For rules governing the proper abbreviation of numbers, see SBLHS §§4.2.4–7 and CMS §9.58–63. Note, however, that SBLHS style always includes all digits in displays of years (e.g., 1970–1975, not 1970–75).
3. Em dashes are used to indicate asides (CMS §§6.82–89).
“I know who you are—the Holy One of God!”
Em dashes can be visually distracting and should be used sparingly. When possible, use commas or parenthesis instead.
4. Three em dashes are used in bibliographies to indicate that subsequent entries are written by the same author or authors.
Moore, Stephen D. The Bible in Theory: Critical and Postcritical Essays. RBS 57. Atlanta: Society of Biblical Literature, 2010.
———. Empire and Apocalypse: Postcolonialism and the New Testament. Sheffield: Sheffield Phoenix, 2006.