A collar is a restraint that is sometimes placed around the neck of bottom partners in BDSM play. It is not uncommon for dominants to wear them as well. Often, submissive partners that regularly wear collars are referred to as being "collared."
At times, formal collaring ceremonies are held. These ceremonies can be likened to wedding ceremonies, with the collar being nearly equivalent to a wedding ring, as they signify the start of a special relationship between a dominant and a submissive.