weakness in a hadith's source (hadith dho'if)

Hadith ; The say, action and admission of the prophet Mohammad (PBUH).
Dho'if ; a weakness.

Hadith Dho'if ; weakness in a hadith's source.

This weakness in hadith's source may happen if the narrator of such hadith isn't fulfil a conditions or requirement to narrate the proved hadith (hadith sohih).

There are 2 conditions regulating to practice this kind of hadith (hukm) ; it shall not related to the conviction ('aqidah) and it shall not used to clarify the Syariah regulations (hukm Syar'e) that is concerning the permissible and illicit in islamic law (halal & haram). furthermore, we should always be aware about the way if we want to narrate this hadith (hadith dho'if), that we shall not narrate this hadith without mentioning the source of this hadith.
but there are some scholars of opinion, on the one hand, this kind of hadith cannot be practiced at all but on the other hand, this hadith is allowed to be practiced relating to the regulations (hukm), benefits (fadhail) besides the conviction ('aqidah) other said it may be practiced relating to the benefits (fadhail) besides conviction ('aqidah) and regulations (hukm).

- we shall not say : "the prophet Muhammad PBUH said........"
- instead : "narrated by "one" : the prophet said........ hadith dhoif"