Obsolescence
Impairment of desirability and usefulness brought about by changes in the art, design or process or from external influencing circumstances that make a property less desirable and valuable for a continuity or use.

Occupancy  
A physical presence within and control of a property.

Occupancy Rate
The percentage of properties in a given area that are occupied.

Offer
A promise by one party to do a specified deed as the other party in turn performs a specific deed.

Office of Comptroller Currency
A federal government regulatory agency that oversees some commercial banks.

Office of Thrift Supervision
A federal government regulatory agency that oversees savings and loans.

Off-site Buildings
Buildings, structures or other amenities which are not located on a piece of property, but are necessary to maximize the use of the property or in some way contribute to the value of the property.

Off- Street Parking
Designated parking spaces associated with a particular building or other structure which are not located on public streets.

On-site Improvments
Buildings, structures or other amenities that are erected on a piece of property and contribute to its value.

On-theme
Refers to content specific to a particular topic

Ontology
As it relates to search, it is the attempt to create an exhaustive and rigorous conceptual schema about a domain. An ontology is typically a hierarchical data structure containing all the relevant entities and their relationships and rules within that domain.