Different categories of hadith have been used by various scholars. Experts in hadith studies generally use two terms - taqrīr for tacit approvals, and khabar for sayings and acts ascribed to Muhammad. The term taqrīr implies that, in the presence of Muhammad, a believer did something, which Muhammad noticed but did not disapprove or condemn. Thus, the act done by a believer acquired tacit approval from Muhammad. It is commonly acknowledged that a khabar can be true or false. The scholars of the science of hadithcriticism hold that a khabar and, therefore, a hadith can be a true report or a concoction. It is on the basis of this premise that the Muslim scholars hold that a hadith offers a ẓannī evidence. It is as though a hadith may have many possibilities on the plane of reliability.
Categorization based on reliability
Ṣaḥīḥ - transmitted through an unbroken chain of narrators all of whom are of sound character and memory. Such a hadith should not clash with a more reliable report and must not suffer from any other hidden defect.
Ḥasan - transmitted through an unbroken chain of narrators all of whom are of sound character but weak memory. This hadith should not clash with a more reliable report and must not suffer from any other hidden defect.
Ḍaʻīf - which cannot gain the status of hasan because it lacks one or more elements of a hasan hadith..
Mawḍūʻ - fabricated and wrongly ascribed to Muhammad.
Maqlūb - It is that hadith, in two different narrations of which the names of narrators have been changed.
Categorization based on number of narrators
Khabar-i mutawatir - A mutawatir hadith is reported by such a large number of narrators that cannot be perceived to have jointly forged and narrated a tradition about an issue without a compelling force. In the opinion of Amin Ahsan Islahi, all such narratives which are usually termed as khabar-i mutawatir should be thoroughly investigated. Islahi is not considered an authority on Hadith within the recognized scholarship of Islam.
Khabar-i wāhid - signifies a historical narrative that falls short of yielding certain knowledge. Even if more than one person reportsthe narrative, that does not make it certain and conclusive truth except when the number of narrators reporting it grows to the level that the possibility of their consensus on forging a lie is perfectly removed.
Classification by epistemic value
In one of the major works in the science of hadith, Al-Khatib al-Baghdadi has divided the individual narratives in the following categories, according to their epistemic value:
