The term configuration item (CI) refers to the fundamental structural unit of a configuration management system.^[1] Examples of CIs include individual hardware or software components. The configuration-management system oversees the life of the CIs through a combination of processes and tools by implementing and enabling the fundamental elements of identification, change management, status accounting, and audits. This system aims to avoid the introduction of errors related to lack of testing as well as of incompatibilities with other CIs.

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The term "configuration item" can be applied to a product, allocated component of a product, or both that satisfies an end use function, has distinct requirements, functionality and/or product relationships, and is designated for distinct control in the configuration-management system. Configuration items and their associated product configuration information versions, and approved changes, form the basis of any current approved configuration audit.

• The entity must be uniquely identified so that it can be distinguished from all other configuration items and their associated product configuration information.
• From the perspective of the implementer of a change, the CI is "what items" within the product structure is effected by the change. Altering a specific baseline version of a configuration item creates a new version of the baseline containing the revise changes to the information impacted by the change. The CI part number may change based on if the new or updated part will no longer be Interchangeable functionally or physically with the existing part. The software CI version will changes for any time a change is implemented. In examining the effect of a change, two of the questions that must be asked are:

1. What configuration items are affected?
2. How have the configuration items and their associated configuration information and interfaces are affected?

• The use of the CI within a product can be traced in a robust status-accounting system.
• The CI is subject to acceptance verification based on established criteria.

In addition to its purpose in the implementation and management of a change, each configuration item's listing and definition should act as a common vocabulary across all groups connected to the product. One should define the CI at a level such that an individual involved with product marketing and an individual responsible for implementation can agree to a common definition when they use the name of the configuration item. Selection and identification of configuration items for a particular project can be seen as the first step in developing an overall architecture of the product from the top down.^{[citation needed]}