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.
However, the relationship between digoxin toxicity and the serum digoxin level is complex. Clinical toxicity results from the interactions between digitalis, various electrolyte abnormalities, and their combined effect on the sodium-potassium adenosine triphosphatase (Na+/K+ ATP ase) pump. Infants and children taking digoxin tolerate higher doses and plasma levels.