5 An operating segment is a component of an entity:

(a) that engages in business activities from which it may earn revenues and incur expenses (including revenues and expenses relating to transactions with other components of the same entity),

(b) whose operating results are regularly reviewed by the entity's chief operating decision maker to make decisions about resources to be allocated to the segment and assess its performance, and

(c) for which discrete financial information is available.

An operating segment may engage in business activities for which it has yet to earn revenues, for example, start-up operations may be operating segments before earning revenues.

6 Not every part of an entity is necessarily an operating segment or part of an operating segment. For example, a corporate headquarters or some functional departments may not earn revenues or may earn revenues that are only incidental to the activities of the entity and would not be operating segments. For the purposes of this IFRS, an entity's post-employment benefit plans are not operating segments.