Sunnah (سنة, plural سنن Sunan) literally means “trodden path,” and therefore, the sunnah of the prophet means “the way and the manners of the prophet”. Terminologically, the word ‘Sunna’ in Sunni Islam means those religious achievements that were instituted by the Islamic prophet Muhammad during the 23 years of his ministry and which Muslims initially obtained through consensus of companions of Muhammad, and further through generation-to-generation transmission. According to some opinions, the sunna in fact consists of those religious actions that were initiated by Abraham and were only revived by Muhammad.
The question of hadith (Arabic: حديث pl. أحاديث, "words and deeds of Muhammad") falling within the abode of the sunna is a disputed one, and is highly dependent on the context. In the context of Islamic Law, Imam Malik and the Hanafi scholars assumed to have differentiated between the sunna and the hadith. In some instances, for example, Imam Malik is supposed to have rejected hadiths that reached him because, according to him, they were against the 'established practice of the people of Medinah'. According to other opinions, sunna constitutes of what Muhammad believed, implied or tacitly approved and was noted down by his companions in form of what is today known as hadith. In Shi'a Islam, the word 'Sunna' means the deeds, sayings and approvals of Muhammad and the twelve Imams who Shi'a Muslims believe were chosen by Muhammad to lead the Ummah - the world muslim community.
In the context of biographical records of Muhammad, sunna indeed often stands synonymous to hadith as most of the personality traits of Muhammad are known through descriptions about him, his sayings and his actions, after becoming a prophet at the age of forty.
