Definition is a rhetorical mode that can be used in something smaller or shorter than a full paper. You can use extended definition for several paragraphs only in a paper of much greater length. You also can add to a paper a one-paragraph definition--like a brief encyclopedia definition.
The research group, headed by Dr. Lukas Sommer at the Swiss Federal Institute of Technology, has identified a heretofore unknown role for the TGF cell-to-cell signaling pathway in the pathogenesis of DiGeorge syndrome.
The signs and symptoms of 22q11.2 deletion syndrome can vary from one affected person to another. For that reason, several disorders and collections of symptoms caused by this syndrome have had other names in the past. These names, some of which are still used occasionally, include: DiGeorge syndrome.