Chapter Seven
On the various ranks of the weak, the authentic, and other categories, together with some of al-Tirmidhī’s special terms

The weak (daʿīf)
A hadith is classified as weak when all—or part—of the conditions required for authenticity or for hasan status are lacking; its transmitter is thereby faulted for irregularity (shudhūdh), aberrance (nakārah), or an underlying defect (ʿillah).

The proliferation of weak categories
From this standpoint, the kinds of weakness multiply and become many, whether considered individually or in combination.