In Indian religions and society, an acharya (Sanskrit: आचार्य, IAST: ācārya; Pali: ācariya) is a preceptor and expert instructor in matters such as religion, or any other subject. An acharya is a highly learned person with a title affixed to the names of learned subject. The designation has different meanings in Hinduism, Buddhism and secular contexts.
Acharya is sometimes used to address an expert teacher or a scholar in any discipline, e.g.: Bhaskaracharya, the expert mathematician.
The Sanskrit phrase Acharam Grahayati Acharam Dadati Iti Va means Acharya (or teacher) is the one who teaches good conduct to one's students. A female teacher is called an achāryā, and a male teacher's wife is called an achāryāni 
In Hinduism, an acharya is a formal title of a teacher or guru, who has attained a degree in Veda and Vedanga.[full citation needed]
Prominent acharyas in the Hindu tradition are as given below :
In Buddhism, an ācārya (Pali: ācariya) is a senior teacher or master. In Theravada it is sometimes used as a title of address for Buddhist monks who have passed ten vassas. In Thai, the term is ajahn, and in Japanese it is ajari.
In Vajrayana Buddhism, tantric masters are known as vajrācāryas (Tibetan: dorje lopön; Jp. “kongō ajari” 金剛阿闍梨).
Main article: Acharya (Jainism)
In Jainism, an acharya is the highest leader of a Jain order. Acharya is one of the Pañca-Parameṣṭhi (five supreme beings) and thus worthy of worship. They are the final authority in the monastic order and has the authority to ordain new monks and nuns. They are also authorized to consecrate new idols, although this authority is sometimes delegated to scholars designated by them.
An acharya, like any other Jain monk, is expected to wander except for the Chaturmas. Bhaṭṭārakas, who head institutions, are technically junior monks, and thus permitted to stay in the same place.
In Sanskrit institutions, acharya is a post-graduate degree.
The role of Guru or Acharya was also very significant in this traditional education system. The word 'Acharya' can be derived as 'Acharam Grahayati Acharam Dadati Iti Va'. It means- Acharya or teacher is that who teaches good behavior to his pupils