A passing mention is any occurrence of a term that does not accompany any substantive discussion of that term. An example of this would be a table that includes a list of terms without any further discussion or description of the terms:
Table 6: Common Herbs
In this case, an index should only include an entry for “herbs” or “herbs, common” depending on the context of the discussion on herbs. To include entries for each herb would clutter the index and provide no useful information to the reader once they located the page referenced. If more information is provided, it may be useful to the reader for this material to be indexed:
Table 7: Uses for Common Herbs
Basil – Can be used dried or fresh in salads and sauces.
Oregano – Can be used dried or fresh. Often used in Mediterranean and Mexican cuisine.
Parsley – Can be used dried or fresh. Often used as a garnish.
Thyme – Often used dried, this distinct herb is a staple in marinara sauce.
In this case, the index might include entries for each herb, such as “basil, common uses,” or “herbs, uses” or “herbs” depending on the text.
Passing mentions can occur anywhere in the text:
“The cuisine of southern Italy often incorporates aromatic herbs such as basil, oregano, parsley, and thyme, as well as tomatoes, fresh pasta, and seafood.”
Here, an index might include an entry such as “southern Italy, cuisine of.” Entries for the individual ingredients would not provide any useful information to the reader.
Passing mentions should never be included in the index.