In the name of Allah, the Most Compassionate, the Most Merciful.
All praise is due to Allah, the Lord of all worlds. May blessings and peace be upon the Seal of the Messengers, our Prophet Muḥammad, upon his family and all his companions, and upon those who follow them with excellence until the Day of Judgement.
To proceed:

This is a concise treatise and a useful introduction to the fundamentals of hadith. I place it before the reader of my commentary on Bulūgh al-Marām, gathering within it the terminology of hadith science that is most needed. I have sought to simplify the rudiments of this discipline, bringing it close to the student of knowledge so that he may pick its blossoms and reap its early fruits with ease and facility. There is no might nor power except with Allah, the Most High, the Most Great.

Hadith Terminology
Definition: The science through which one comes to know the state of both the transmitter and the transmitted report in terms of acceptance and rejection.
Benefit: To discern which narrations are to be accepted and which are to be rejected by distinguishing the sound from the weak.
Sources: The material of this science is drawn from the conditions of a hadith’s text, the conditions of its transmitters and their transmission, and the investigation of those conditions.

Definitions
• Ḥadīth and khabar: synonymous; each refers to whatever is attributed to the Prophet ﷺ by way of word, deed, or tacit approval.
• Isnād and sanad: synonymous; each denotes the chain of men that leads to the text.
• Matn: the wording at which the chain terminates.

Classification of hadith according to its lines of transmission
Hadith falls into two categories: mutawātir and āḥād.
Mutawātir: a report that has reached us through transmission routes whose number is not fixed—namely, one narrated by such a multitude that it precludes—