Lineaged Wicca is organized into covens of initiated priests and priestesses. Covens are autonomous, and are generally headed by a High Priest and a High Priestess working in partnership, being a couple who have each been through their first, second and third degrees of initiation. Occasionally the leaders of a coven are only second-degree initiates, in which case they come under the rule of the parent coven. Initiation and training of new priesthood is most often performed within a coven environment, but this is not a necessity, and a few initiated Wiccans are unaffiliated with any coven.
A commonly quoted Wiccan tradition holds that the ideal number of members for a coven is thirteen, though this is not held as a hard-and-fast rule. Indeed, many U.S. covens are far smaller, though the membership may be augmented by unaffiliated Wiccans at "open" rituals. When covens grow beyond their ideal number of members, they often split (or "hive") into multiple covens, yet remain connected as a group. A grouping of multiple covens is known as a grove in many traditions.
Initiation into a coven is traditionally preceded by a waiting period of at least a year and a day. A course of study may be set during this period. In some covens a "dedication" ceremony may be performed during this period, some time before the initiation proper, allowing the person to attend certain rituals on a probationary basis. Some solitary Wiccans also choose to study for a year and a day before their self-dedication to the religion.