All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His Slave and Messenger.
The technical definition of a term refers to the meaning of that term in a given discipline. The claim that all the scholars of different disciplines and areas of knowledge agree on one specific technical meaning of a given term is untrue. The term Sunnah, for example, in its technical sense has different technical meanings in the Hadeeth, Fiqh (Islamic jurisprudence), and Usool Al-Fiqh (principles of Islamic jurisprudence) traditions. The scholars of Hadeeth define the term Sunnah differently from how the scholars of Usool Al-Fiqh and Fiqh define it.
In Hadeeth terminology, the term Sunnah refers to the sayings, actions, approvals (tacit or explicit) and attributes attributed to the Prophet, whether physical or moral, regardless of whether or not it can be used as evidence in a legal ruling.
In the terminology of Usool or principles of jurisprudence, Sunnah refers to the sayings, actions and approvals of the Prophet that serve as evidence in religious rulings.
In the terminology of Fiqh or jurisprudence, Sunnah refers to whatever the Prophet commanded by way of recommendation and not obligation (i.e. whoever does it is rewarded and whoever does not is not punished). For more benefit, please refer to Fatwa 146195.
Allaah Knows best.