Q. I have a question about line breaks. I work a lot with German authors and German presses (and then also German conventions and German passages in the texts I am editing). In German, one is supposed to avoid ending a line with a period that is not at the end of a sentence. This means anytime a period is used for an abbreviation, it should be followed by a nonbreaking space so that it will not appear at the end of a line. The idea is that this prevents the reader from misreading the period as the end of the sentence. If I understand correctly, Chicago does not suggest a similar convention for line breaks, correct? Thank you for your reply!
A. You are right. Though CMOS covers line breaks in English (in chapter 7) and a few other languages (including German, in paragraphs 11.42, 11.43, and 11.44), we don’t include any recommendation that says you must carry an abbreviation that ends in a period over to the next line when the sentence continues beyond the abbreviation.
So a line is allowed to end with an “a.m.” or “Jr.” or the like that occurs in the middle of a sentence. But there are some exceptions. For example, the initials in a name like P. D. James are best kept together with a nonbreaking space (see CMOS 6.121), and some typesetters will use a nonbreaking space to prevent a compound like “St. Louis” or “Dr. Smith” from breaking at the end of a line.
And if an author or typesetter wanted to apply the convention you describe for passages of German text in one of our English-language publications, we wouldn’t object. For one thing, the convention seems well suited to German, where all nouns are capitalized, making it more difficult to recognize that a word following a period isn’t necessarily the beginning of a new sentence. Those who don’t read German won’t notice; those who do read it might appreciate the nicety.