"Sunnah" (pl. sunan): method, line of conduct, good or bad, nature, destination.
Books of Hadith that collect the Hadiths narrated by each Companion individually.
Books containing Hadiths that meet the conditions of one of the Hadith compilers, but that are not included in his work.
Books of Hadith that include Hadiths related to juristic rulings and many citations reported from the Companions and "Tābi‘is" (generation following that of the Companions).
Books that compile extra Hadiths and add them to other book or books.
Groups of the Companions who share certain conditions and qualities.