An omission of two or more consecutive narrators at any point in the chain is al-muʿḍal.
An omission from the start of the isnād by the compiler's action — this is al-muʿallaq.
If the narrators of a ḥadīth agree in their wording of transmission, in any verbal feature, in an action, or in some shared quality, this is al-musalsal (literally, a chained or serial ḥadīth).
When narrators' names are identical in writing but differ in pronunciation, this is al-muʾtalif wa-l-mukhtalif.
The rejected report falls into two kinds: that rejected because of an omission in the isnād, and that rejected because of criticism of the narrator.
