O-ring
A small rubber ring that provides a water seal in faucets and other plumbing fittings.

Obsolescence
Loss in value because a home's design and construction have become obsolete.

Online real estate listings
Properties, Real Estate or Land that are listed for sale on the Internet.

Open house
A marketing tool in which a listing agent opens a house for view.

Open listing
A property given to a number of brokers to market at the same time.

Open space
Undeveloped land or common areas in a planned community reserved for parks, walking paths or other natural uses.

Option
A situation in which a buyer puts down money for the right to purchase a piece of real estate within a set time period but does not have an obligation to buy.

Option listing
A listing agreement with a clause that gives the listing broker the right to purchase the property.

Oral agreement
Contractual arrangements that are not in writing and are usually not legally binding.

Orange peel
A type of wallboard finish with a texture like that of an orange peel.

Oriented-strand board
Often abbreviated "OSB," this is a relatively inexpensive manufactured wood panel that, like plywood, is sold typically in a 4-by-8-foot size and used for roof and wall sheathing.

Original principal balance
The amount of principal owed on a loan before a borrower makes any payments.

Original Principle Balance
The total amount of principal owed on a mortgage before any payments are made.

Origination Fee
On a government loan the loan origination fee is one percent of the loan amount, but additional points may be charged which are called "discount points." One point equals one percent of the loan amount. On a conventional loan, the loan origination fee refers to the total number of points a borrower pays.

Ostensible agency
An implied agency relationship not involving a written agreement or documentation.

Outbuilding
Any barn, shop, shed, or other structure located on a lot in addition to a house or other main building.

Overflow plate
A small plate that covers an outlet near the rim of a sink or tub. If the water is left running, this allows it to drain away to prevent overflows.

Overflow prevention switch
A special air-pressure switch in a dehumidifier that turns the unit off when water in the reservoir rises to a certain level.

Overhang
A protruding structural feature.

Overimproved property
Property that could not be sold at a price high enough to recoup the costs of improvements.

Owner Financing
A property purchase transaction in which the property seller provides all or part of the financing.

Owner's Title Policy
A policy protecting the buyer for the amount of the purchase price in the event of a future title dispute.