The abbess is the head of a community of nuns, elected by its members and holding within her house the same governing authority that an abbot holds within his.
Elected and governing
The abbess is chosen by the professed members of the community and rules its life and discipline as its mother and superior, exercising a real jurisdiction over the internal affairs of the monastery, so that within the enclosure her authority is complete in the way the abbot is within his. The office is ancient, and in the medieval period some abbesses ruled great and wealthy houses and wielded considerable temporal power, a few holding an authority over lands and even clergy that was remarkable for women of their time.
The limit of the office
The authority of the abbess is one of government and jurisdiction rather than of holy orders, for a woman cannot be ordained in the churches that maintain the office, so the abbess governs and disciplines her community but does not perform the priestly acts, which require a priest brought to the monastery. Within that limit her rule over the house is genuine and her election by the community makes her, like the abbot, the elected head of an autonomous body rather than an appointee from outside. The office is the female counterpart of the abbot, and it has been one of the principal positions of real authority open to women across the history of the church.