Q. I can’t locate an answer to this question. Are proper names with particles alphabetized based on the particle or the first element? I.e., which comes first, “da Rosa” or “Dario”?

A. If you’re alphabetizing letter by letter, put “Dario” first (“d-a-r-i” comes before “d-a-r-o”); under the word-by-word system, “da Rosa” would go first (“da” comes before “Dario”). In either system, the particle is alphabetized along with the name unless the surname is normally listed without the particle. So, for example, Simone de Beauvoir would be listed before an individual with the last name da Rosa even though “de” would follow “da”—because Beauvoir is generally referred to by surname alone, without the particle (and would be listed as “Beauvoir, Simone de” in an index). See CMOS 16.71 for more examples.