Q. When using a preceding -ly adverb to modify an adjective, it typically pains me to use an open form (no hyphenation). But I bite the bullet, follow CMOS, and eliminate the hyphen. Yet when there are two essentially equivalent formulations where one adverb is an -ly adverb and the other is not, I’m perplexed as to the logic. For instance: She had a nearly encyclopedic knowledge of baseball statistics versus She had an almost-encyclopedic knowledge of baseball statistics. Can you provide any insights? Thank you.
A. Okay, so you have a deeply-rooted dislike—as Jane Austen’s publisher styled that phrase in the 1813 first edition of Pride and Prejudice, vol. 2, p. 124—for the modern rule that says that you should write deeply rooted dislike (as covered in CMOS 7.96, section 2, under “adverb ending in ‑ly + participle or adjective”). We’re not offended. The idea that readers will expect an adjective rather than a noun after a word like deeply and thus don’t need any help from a hyphen could easily be turned on its head. You could argue instead that the adverb and participle clearly belong together and should go ahead and tie the knot (with a hyphen).
But if you do follow Chicago style, don’t worry about being inconsistent in the examples you cite. Our editors would tend to leave the compound modifiers in both of your sentences open: a nearly encyclopedic knowledge and an almost encyclopedic knowledge. See CMOS 7.96, section 2, but this time under “adverb not ending in ‑ly + participle or adjective,” which notes that “certain compounds, including those with more, most, less, least, and very, can usually be left open unless ambiguity threatens.”
As one of the examples in that category suggests (“a rather boring play”), you can extend this exception to other adverbs of degree, including not only rather but also almost.
We’ll make a note to consider clarifying this in a future edition of CMOS. It’s less likely, however, that we’ll be revising our rules to be more in line with nineteenth-century hyphenation conventions.