An enterprise may go to a lot of trouble to develop definitions. Some degree of standardization across these definitions is helpful. One aspect of standardization is dealing with terms that appear in definitions. Terms can be divided into two classes: Common Terms, which widely understood, and require no definition; and Defined Terms, which signify the concepts that the enterprise is defining.
A major rule in definitions is that the term signifying the concept should not appear in the definition. This is a good idea for summary definitions, but it is hard to justify in full definitions. Thus, if one component of a definition is a summary, it is best to keep the term being defined out of the summary. However, the term should be allowed elsewhere in the definition.
Common terms should be allowed in a definition with no special formatting. There is no need to distinguish them as something special. Indeed, this would be misleading.
Defined Terms (either the term being defined, or terms defined elsewhere by the enterprise) should be distinguished. One reason is that terms composed of many words may not easily be understood to form a single term. E.g. "The project code management team should be contacted". Perhaps this refers to a team that manages project codes ("Project Code management team") or perhaps it is a team that manages code for a project ("project Code Management team"). A common way to distinguish Defined Terms is to capitalize them. This makes it easier for the reader to understand they are a defined term (versus common term), and also to understand that a series of words forms one term. Another approach is to make defined terms bold. However, this tends to indicate emphasis rather than the presence of a defined term, and may be disagreeable to readers. Underlining and italics are also used to indicate emphasis, but may sometimes be a convention for defined terms, as in biological species names, e.g. Panthera leo.
Defined Terms can also be turned into hyperlinks in definition repositories. This clearly distinguishes them. Usually this is an automated feature, so Common Terms can get hyperlinked too if they are included in the repository. Therefore governance is required to keep Common Terms out of the repository.