NIM terms are concepts that are discussed but are not the main point of the article. Some common concepts which are frequently NIM are:
- Techniques/research methods (MICROSCOPY, ELECTRON)
- Animals studied experimentally (RATS)
- Terms that further specify an IM term (CHRONIC DISEASE)
However, these concepts can be indexed IM if they are the main focus of the article. Remember that the selection of a term as IM or NIM depends on the importance of the concept in the article.
It is important to understand, that terms which are usually used as NIM, can, sometimes, be indexed as IM concepts. For example, an article about chronic gastritis will be indexed with the terms GASTRITIS as IM and CHRONIC DISEASE as NIM. However, an article about chronic disease in general will be indexed with the term CHRONIC DISEASE as an IM concept.
The same rationale applies to concepts usually indexed as IM – in some circumstances they will be indexed as NIM.
Many articles can be adequately indexed with 15 or fewer NIM terms. It is important that an indexer should use as many NIM terms as needed but not add terms simply to reach a number.
Not every concept mentioned in an article is indexed. Concepts should only be indexed if they are discussed and not merely mentioned in an article.