The reduction or abatement of rent owed to a landlord as a result of a tenant not receiving an essential item that is the responsibility of the landlord to provide under the lease or for an expenditure made by the tenant in order to remedy the failure of the landlord to provide required and essential item as contained within the lease. For example, a tenant who buys a heater in order to supply heat to the premises during an extended time that the heating system for the premises was in a nonworking condition.