It is the science of those laws whereby the condition of the sanad [chain of transmission] and matn [text of the ḥadīth] is known. Its objective is to differentiate the sahīh hadīth from the others. It is of two types: the science of hadīth pertaining to transmission [riwāya] and the science of the hadīth pertaining to meaning [dirāya]. As for the one pertaining to transmission, it includes the transmission of the sayings of the Prophet , his actions, consent and attributes, with repsect to their narration, accuracy and transcription of words [tahrīr alfādh]. As for the one pertaining to the meaning, the reality, conditions, types and rules of transmission are known through it, as well as the state of the transmitters, their conditions, the types of the transmissions and that which is related to it. Dirāya also covers knowledge of the meaning contained in the hadīth in terms of whether it contradicts a definitive text.