It is whatever does not meet the conditions of tawātur.
Khabar al-wāḥid yields presumption (ẓann) in every case, although the grades of presumption vary.1
It has three sub-categories based on the number of narrators.2
This is the position of the majority. According to al-Samʿānī, al-Āmidī, Ibn al-Ṣalāḥ, Ibn Taymiyya, al-Bulqīnī, Ibn Ḥajar, al-Suyūṭī, and others, however, some solitary reports may yield theoretical (acquired) knowledge through supporting indications (qarāʾin). See: Qawāṭiʿ al-Adilla, 1/332–333; Muntahā al-Sūl, p. 79; Sharḥ Nukhbat al-Fikr, pp. 17–22; Tadrīb al-Rāwī, 1/131–134. ↩
Sharḥ Nukhbat al-Fikr, p. 15. ↩
Ḥadīth, in the muḥaddithūn's classification, is of two categories: al-mutawātir and khabar al-wāḥid.
Al-mutawātir is a ḥadīth narrated, on the basis of sensation rather than pure reason, by a number whose collusion upon falsehood is rendered impossible by ordinary custom.
The Ḥanafīs treat al-mashhūr as a third tier alongside al-mutawātir and khabar al-wāḥid, defined by what was āḥād in the first generation but tawātur thereafter.
When the narrators' names are the same but their fathers' names differ, or vice versa, this is al-mutashābih; from it and the preceding categories various sub-types are formed.
