occupancy

n. act of occupying; state of being an occupant; period of residence; act of taking possession (Law); right of possession

Occupancy is a defined legal term in building construction and building codes. It refers to the use or intended use of a building or part thereof for the shelter or support of persons, animals or property. A closely-related meaning is the number of units in such a building that are rented or leased, or otherwise in-use. The lack of occupancy in this sense is a vacancy.
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Noun
1. an act of being a tenant or occupant
(synonym) tenancy
(hypernym) residency, residence, abidance
(hyponym) inhabitancy, inhabitation, habitation
(derivation) occupy, reside, lodge in
2. the act of occupying or taking possession of a building; "occupation of a building without a certificate of occupancy is illegal"
(synonym) occupation, taking possession, moving in
(hypernym) acquiring, getting
(hyponym) preoccupancy, preoccupation
(derivation) inhabit, occupy

(n.)
The act of taking or holding possession; possession; occupation.
  

For equipment, such as a circuit or a switch, the ratio of the actual time in use to the available time during a 1-hour period. Note 1: Occupancy is usually expressed in percent. Note 2: Occupancy may be plotted versus time of day. Synonym usage.