What is the true definition of a scholar, and how can one differentiate between a scholar and a preacher or orator? Are there levels of scholars, and can the specializations of scholars be classified?

A scholar is an expert in the religion of Allah. Beneficial knowledge instills awe (khashyah), and awe of Allah is sufficient as knowledge. Knowledge is not about extensive narration, but about awe and action. The most virtuous scholar is one who propagates knowledge after fulfilling the obligatory duties and the Sunnah. The most severely punished person is a scholar whose knowledge did not benefit him, for knowledge is what benefits, not what is memorized. A scholar possesses personal qualities such as good conduct and guidance, and he should be a caller to Allah with clear insight. In later times, the term "scholar" became predominantly associated with those who teach and issue fatwas, while "caller to Islam" (da'i) referred to one who interacts with people to unite them upon Islam, and "preacher" (wa'iz) to one who ignites hearts with remembrance. People have varying degrees of knowledge, from the absolute mujtahid to the muqallid (imitator), and knowledge has been compiled, books have been authored, and specializations have emerged.