Overview
In Indian religions and society, an acharya (Sanskrit: आचार्य, IAST: ācārya; Pali: ācariya) refers to a religious teacher and spiritual guide. The term is used in both Hinduism and Buddhism, and carries somewhat different connotations across these traditions as well as in secular usage.
Within Hindu tradition, an acharya is regarded as a teacher who imparts knowledge of sacred texts and guides disciples in matters of doctrine, ritual and conduct. In Buddhism, the corresponding Pali term ācariya denotes a teacher who instructs students in scripture and practice, often alongside a preceptor.
Beyond strictly religious settings, the title acharya is also applied more broadly as an honorific for an accomplished scholar or expert teacher in any discipline. A well-known example is the mathematician Bhaskaracharya, whose name incorporates the title in recognition of his scholarly stature.
References
Adapted from the English Wikipedia article on Acharya.