The omission may be from the start of the isnād by the compiler's action; this is al-muʿallaq.
An omission of two or more consecutive narrators at any point in the chain — this is al-muʿḍal.
Al-mawqūf (literally, halted) consists of the sayings and actions of the Companions, may Allāh be pleased with them.
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.
