Priests of the Vedic religion were officiants of the yajna service. As persons trained for the ritual and proficient in its practice, they were called ("regularly-sacrificing"). As members of a social class, they were generically known as vipra ("sage") or kavi ("seer").
Specialization of roles attended the elaboration and development of the ritual corpus over time. Eventually a full complement of sixteen s became the custom for major ceremonies. The sixteen consisted of four chief priests and their assistants, with each of the four chief priests playing a unique role:
The was the reciter of invocations and litanies. These could consist of single verses (), strophes (triples called or pairs called pragātha), or entire hymns (sukta), drawn from the . As each phase of the ritual required an invocation, the had a leading or presiding role.
The adhvaryu was in charge of the physical details of the sacrifice (in particular the adhvara, a term for the Somayajna). According to Monier-Williams, the adhvaryu "had to measure the ground, to build the altar, to prepare the sacrificial vessels, to fetch wood and water, to light the fire, to bring the animal and immolate it," among other duties. Each action was accompanied by supplicative or benedictive formulas (yajus), drawn from the yajurveda. Over time, the role of the adhvaryu grew in importance, and many verses of the were incorporated, either intact or......