Which statement best describes the relationship between indexing units and key units in the examples?

• A. The key unit is always the surname
• B. The key unit is always the first letter of the surname
• C. The key unit can be the surname or a single initial, depending on the example
• D. There is no concept of a key unit

Answer: (C)

Indexing relies on choosing a primary access point from the data you’re organizing. The indexing unit is the data element you consider when building the index, while the key unit is the element you actually use for sorting and retrieval. Because different examples follow different cataloging rules, the key unit isn’t fixed. In some cases the surname serves as the key unit, giving a straightforward surname-based access point. In other cases, especially when distinguishing among people with the same surname or when only an initial is available, a single initial can be the key unit. So the relationship is flexible: the key unit can be the surname or a single initial, depending on the example and the rule being applied.