HabitatReporter here with advice from Edward T. Braverman, Esq., of Braverman & Associates , P.C.:

"A tenant is one who has a contractual relationship with the landlord. In Co-op parlance, that would mean one who is named in and who has executed a Proprietary Lease. A roommate is legally considered to be an occupant: a person who occupies the housing accommodation with the consent of the tenant. Under New York Law every tenant is entitled to have a roommate to whom the landlord (Co-op) cannot object. A subtenant is one who has a formal agreement with the tenant, who (the tenant) has assigned his lease rights to the subtenant, subject to all of the terms and conditions of the lease (Proprietary Lease) with the express written consent of the landlord. His sublease must be something less than the full term of the lease so that the occupancy of the apartment reverts to the tenant of record prior to its expiration. A spouse who is an occupant, while not a tenant, generally will be entitled to receive the transfer of the apartment upon the tenant’s death without the consent of the Co-op’s Board of Directors."