sayyidina muhammad (pbuh) said in his last khutbah at arafat:
all those who listen to me shall pass on my words to others and those to others again; and may the last ones understand my words better than those who listen to me directly.
sahifah is a collection of ahadeeth of sayyidina muhammad as written down by one of his companions. collection of abdullah bin al-aas known as sadiqah is an example.
it is a large collection of ahadeeth in which ahadeeth relating to different topics are put together and arranged in chapters dealing with a particular topic. muwatta of imam malik, sahih bukhari and sahih muslim are examples of this kind.
the word musnad (supported) was originally used for ahadeeth which were supported by a complete uninterrupted chain of narrators going back to a companion who related it from sayyidina muhammad. but later on the term came to used in a more general sense of reliable and authoritative ahadeeth. in this sense the term is also used for all reliable works of hadeeth literature, and the works like sunan of al-darimi and sunan of al-bukhari may be called musnads. but technically, it is used only for those collections of ahadeeth in which they are arranged in accordance to the names of the final authorities by whom they are related irrespective of their subject matter.
sunan are collections of ahadeeth relating to al-ahkam (legal injunctions). the collection prepared by imam abu dau’d (ra), imam nasa’i (ra), and others are known as sunan works.
the term mu’jam is commonly applied to such works on various subjects which are arranged in alphabetical order. the collections which are arranged under the names of the companions in alphabetical order are also known as mu’jam al-sahaba. but according to the authorities of the science of hadeeth the term is technically used for such collections of ahadeeth which in fact have been arranged according to the muhadditheen from whom the compiler himself received them. collections belonging to this class are tabrani, ibn al-qani.
the ijzah are collections of ahadeeth that have been handed down on the authority of one single individual whether he be a sahabi (companion) or a taba’ee (successor).
these are collection of ahadeeth which deal with one particular topic out of the following eight topics into which the contents of the jam’i books of ahadeeth may be classified:
a) aqaaid (beliefs).
b) ahkam (laws).
c) ruqaq (peity, asceticism, mysticism etc.)
d) aadaab (etiquettes in eating, drinking, travelling etc.)
e) tafsir (commentary of the holy qur’an).
f) tarikh or siyar (historical or biographical matters which include cosmology, ancient history, life of sayyidina muhammad companions and successors.
g) fitan (trials and tribulations).
h) appreciation and denunciation of persons and places.
the rasa’il are also called kutub (books). the works of ibn hajar al-asqalani and jalaluddin suyuti belong to this category.
these are collections of ahadeeth in which the complier has accepted the conditions laid down by previous compilers, and adds ahadeeth left by the original compilers for some reason. mustadrak of hakim belongs to this category who increased the ahadeeth in the works of bukhari and muslim which were originally not included by them in their sahihs.
mustakhraj are those collections of ahadeeth in which a later compiler adds fresh isnads (chains of narrators) to the traditions already collected by previous compilers. abu nu’aym isfahani wrote a mustakhraj on the sahih of imam bukhari and imam muslim by adding fresh chains of narrators for some of the traditions which were already included by them in their sahihs.
jami’ are those collection of ahadeeth which contain ahadeeth relating to various subject matters mentioned under rasa’il. sahih bukhari and tirmidhi are examples of this category.
arba’eenat as the name suggests are the collections of forty ahadeeth relating to one or more subjects which may have appeared of special interest to the compiler.
the arba’een of imam nawawi (ra) is an example of this kind.
this is in obedience to the hadeeth of sayyidina muhammad:
“whosoever of my ummah commits to memory forty ahadeeth regarding religious matters, he will be raised with the jurists and religious scholars on the day of judegement”