Q. Dear CMOS, As regards a foreign word that needs to remain in its original language in a lengthy comparative analysis, would you inflect this word so as to reflect its grammatical position in a sentence consistent with its inflection in the original language? The word at issue is Pflichtteilsberechtigter (roughly, a forced heir). In its original German, the singular of the word could be either Pflichtteilsberechtigte or Pflichtteilsberechtigter, depending on whether it is preceded, respectively, by a definite or an indefinite article. As a plural, it could be either Pflichtteilsberechtigten or Pflichtteilsberechtigte, depending on whether it is preceded, respectively, by a definite article or a zero article.
Consistent with German grammar, the word would be spelled/inflected as follows in these four sample sentences (the first two being singular usages and the second two plural usages): “A Pflichtteilsberechtigter enjoys special rights in German succession law. The Pflichtteilsberechtigte, the son of the deceased, sued the testamentary heir for a portion of the estate. Courts require Pflichtteilsberechtigte to submit certain forms. In the case at issue, the court required the Pflichtteilsberechtigten to first appear before a notary.”
Employing spellings consistent with German grammatical rules on inflection could potentially confuse readers unfamiliar with these rules (or leave them thinking the writer/editor has been careless!). But adopting a wholesale simplification (e.g., writing Pflichtteilsberechtigter whenever it is a singular usage and Pflichtteilsberechtigte whenever it is a plural usage and not further inflecting according to German grammar) could confuse—or at least annoy—those readers who will have an appreciation of German, which will likely be significant in this case. We look forward to any input you have to offer!
A. Extrapolating from CMOS 11.3, it’s usually best to inflect a non-English word that hasn’t been anglicized just as it would be in the original language, as when referring to more than one Blume (flower) as Blumen (flowers).
Accordingly, the examples in your second paragraph seem good to us, with one possible caveat. Out of context, it may not be obvious to all readers that “the Pflichtteilsberechtigten” in your last sentence is supposed to be plural. If necessary, you could rephrase—for example, as “each Pflichtteilsberechtigte,” where the German noun is now clearly singular (and inflected as it would be following the)—or whatever best conveys the intended meaning.
But you should consider explaining for your readers how these inflections work—for example, in a note the first time one of these terms appears in your text. The explanation near the beginning of your question (“In its original German, . . .”) could easily form the basis of such a note.