1) The knowledge of i'tibar, mutaba'a and shahid. Traditionists are always in search of more witnesses in favour of a hadith which is reported by one source only; such research is termed i'tibar. If a supporting narration is not found for a particular hadith, it is declared as fard mutlaq (absolutely singular) or gharib. For example, if a hadith is reported through the following isnad: Hammad b. Salama --- Ayyub --- Ibn Sirin --- Abu Huraira --- The Prophet, research would be done to ascertain whether another trustworthy reporter has narrated it from Ayyub; if so, it will be called mutaba'a tamma (complete mutaba'a); if not, a reporter other than Ayyub narrating from Ibn Sirin would be sought: if so, it will be called mutaba'a qasira (incomplete mutaba'a).
2) Afrad (singular narrations).
3) The type of character required in an acceptable reporter.
4) The way a hadith is heard and the different ways of acquiring ahadith.
5) How a hadith is written and how punctuation marks are used.
6) The way a hadith is reported.
7) The manners required in traditionists.
8) The manners required for a student of hadith.
9) The knowledge of a higher or lower isnad (i.e. one with less or more reporters respectively).
10) The knowledge of difficult words.
11) The knowledge of abrogated ahadith.
12) The knowledge of altered words in a text or isnad.
13) The knowledge of contradictory ahadith.
14) The knowledge of an addition made to an isnad (i.e. by an inserting the name of an additional reporter).
15) The knowledge of a well-concealed type of mursal.
16) The knowledge of the Companions.
17) The knowledge of the Successors.
18) The knowledge of elders reporting from younger reporters.
19) The knowledge of reporters similar in age reporting from each other.
20) The knowledge of brothers and sisters among reporters.
21) Knowledge of fathers reporting from their sons.
22) Knowledge of sons reporting from their fathers.
23) Knowledge of such reporters reporting from one authority, one in his early life and the other in his old age. In such cases the dates of death of the two reporters will be of significance.
24) Knowledge of such authorities from whom only one person reported.
25) Knowledge of such reporters who are known by a number of names and titles.
26) Knowledge of unique names among the Companions and the reporters in general.
27) Knowledge of names and by-names (kunya).
28) The knowledge of by-names for reporters known by their names only.
29) The knowledge of nicknames (alqab) of the traditionists.
30) Knowledge of mu'talif and mukhtalif (names written similarly but pronounced differently, e.g. Kuraiz and Kariz.
31) The knowledge of muttafiq and muftariq (similar names but different identities), e.g. "Hanafi": there are two reporters with this name; one is called by this name because of his tribe Banu Hanifa; the other because of his adherence to a particular madh-hab.
32) Names covering both previous types.
33) Names looking similar but they differ because of the difference in their father's names, e.g. Yazid b. al-Aswad and al-Aswad b. Yazid.
34) Names attributed to other than their fathers, e.g. Isma'il b. Umayya; in this case Umayya is the mother's name.
35) Knowledge of such relations (attributed to a place or tribe, etc.) which have a meaning different from what they seem to be apparently, e.g. Abu Mas'ud al-Badri, who is known as al-Badri not because he witnessed the battle of Badr but because he came to live there.
36) The knowledge of ambiguous reporters by finding out their names.
37) The knowledge of the dates of birth and death of reporters.
38) The knowledge of trustworthy and weak reporters.
39) Knowledge of such trustworthy reporters who are found to be confused in their old age.
40) Knowledge of contemporaries in a certain period.
41) The knowledge of free slaves (mawali) among the reporters.
42) The knowledge of the homelands and home towns of reporters.