• al-muʿallal (defective): a report that harbors a subtle flaw which undermines its authenticity even though, outwardly, it appears sound. The defect is usually the result of an error made by the transmitter.
The way to determine the status of such a ḥadīth and to uncover the defect is to gather all its chains of transmission, then examine the variations among the narrators and the degree of their precision.
The flaw may lie in the text (matn) or, more commonly, in the chain (isnād).

• al-muḍṭarib (irregular): a report transmitted in mutually contradictory versions that cannot be reconciled, while the competing routes are equal in strength. The irregularity may affect the text or, more often, the chain.

Classifications of ḥadīth according to the one to whom it is ascribed
• al-marfūʿ (traced back to the Prophet): whatever is attributed to the Messenger of Allah ﷺ—whether a statement, an action, or a tacit approval—regardless of whether the chain is continuous or interrupted.
• al-mawqūf (Companion report): whatever is attributed to a Companion, with or without a continuous chain.
• al-maqṭūʿ (Successor report): whatever is attributed to a Successor or anyone below him, whether the chain is connected or broken.
• al-musnad: a report whose chain is uninterrupted all the way to the Prophet ﷺ.

Benefit: al-maqṭūʿ is not the same as al-munqaṭiʿ; the first describes the nature of the text, whereas the second describes a break in the chain.

Types of compilations in ḥadīth studies
• al-jāmiʿ (comprehensive collection): a work whose author gathers reports covering creed, legal rulings, etiquette, exegesis, biography, virtues, and other subjects—such as Ṣaḥīḥ al-Bukhārī.
• al-musnad: a compilation arranged according to the Companions, so that all the reports of each Companion are presented together without regard to topic. The most famous of the musnads