This document discusses the science of hadith terminology (mustalah al-hadith). It defines mustalah al-hadith as the collection of principles to determine the authenticity of a narrator or narration attributed to the Prophet Muhammad. It outlines the different types of narrations including hadith, khabar, athar, and hadith qudsi. It also provides a brief biography of the author, Shaykh Muhammad ibn Saalih al-‘Uthaymeen.