The Book of Mormon stands out from pseudo-archaic texts in both types and number of instances of subordinate that.
The longer pseudo-archaic texts, which together have more than twice as many words as the Book of Mormon, have fewer types of subordinate that, as well as fewer instances.
Taken together, the 12 longer pseudo-archaic texts have half as many types and about one-fifth the rate of occurrence (1.2 instances per about 10,000 words versus 6.9 per 10,000 words in the Book of Mormon, which has approximately 250,000 words in mostly nonbiblical contexts).
Table 1. Comparison of archaic subordinate that usage with eight subordinators in the King James Bible, the Book of Mormon, and 25 pseudo-archaic texts.
King James Bible Book of Mormon Pseudo-Archaic Texts after that S ✓ ✓ ✓ how that S ✓ ✓ ✓ because that S ✓ ✓ ✓ for that S ✓ ✓ ✓ before that S ✓ ✓ lest that S ✓ ✓ until/till/to that S ✓ ✓ Since that S ✓ Note: Five other subordinating conjunctions discussed in Grammatical Variation (see note 6) — “except (that) S”, “insomuch (that) S”, “notwithstanding (that) S”, “save (that) S”, and “than (that) S” — were not included in this study, either because the degree of archaism of the that-construction isn’t clear or the lack of that is often due to other grammatical factors. The correlation of the subordinate that usage of the King James Bible and the Book of Mormon is 0.78.
(Stanford Carmack, “A Comparison of the Book of Mormon’s Subordinate That Usage,” Interpreter: A Journal of Latter-day Saint Faith and Scholarship, Vol. 50 (2022), pp. 1-32, https://journal.interpreterfoundation.org/a-comparison-of-the-book-of-mormons-subordinate-that-usage/)