Office automation refers to the varied computer machinery and software used to digitally create, collect, store, manipulate, and relay office information needed for accomplishing basic tasks. Raw data storage, electronic transfer, and the management of electronic business information comprise the basic activities of an office automation system. Office automation helps in optimizing or automating existing office procedures.

Old age consists of ages nearing or surpassing the average life span of human beings, and thus the end of the human life cycle. Euphemisms and terms for old people include, old people (worldwide usage), seniors (American usage), senior citizens (British and American usage), older adults (in the social sciences), the elderly, and elders (in many cultures including the cultures of aboriginal people).

Oncology is a branch of medicine that deals with the prevention, diagnosis, and treatment of cancer. A medical professional who practices oncology is an oncologist. The name's etymological origin is the Greek word ὄγκος (ónkos), meaning "tumor", "volume" or "mass" and the word λόγος (logos), meaning "speech".

One-switch games are games that can be played using switch access and which accommodate the abilities of users with severe motor impairments or cognitive impairments.

Online chat may refer to any kind of communication over the Internet that offers a real-time transmission of text messages from sender to receiver. Chat messages are generally short in order to enable other participants to respond quickly. Thereby, a feeling similar to a spoken conversation is created, which distinguishes chatting from other text-based online communication forms such as Internet forums and email. Online chat may address point-to-point communications as well as multicast communications from one sender to many receivers and voice and video chat, or may be a feature of a web conferencing service.

Open-source hardware (OSH) consists of physical artifacts of technology designed and offered by the open design movement. Both free and open-source software (FOSS) as well as open-source hardware is created by this open-source culture movement and applies a like concept to a variety of components. It is sometimes, thus, referred to as FOSH (free and open source hardware). The term usually means that information about the hardware is easily discerned so that others can make it - coupling it closely to the maker movement. Hardware design (i.e. mechanical drawings, schematics, bills of material, PCB layout data, HDL source code and integrated circuit layout data), in addition to the software that drives the hardware, are all released under free/libre terms. The original sharer gains feedback and potentially improvements on the design from the FOSH community. There is now significant evidence that such sharing creates enormous economic value.

The open-source model is a decentralized development model that encourages open collaboration. A main principle of open-source software development is peer production, with products such as source code, blueprints, and documentation freely available to the public. The open-source movement in software began as a response to the limitations of proprietary code. The model is used for projects such as in open-source appropriate technologies, and open-source drug discovery.

An operating system (OS) is a collection of software that manages computer hardware resources and provides common services for computer programs. The operating system is an essential component of the system software in a computer system. Application programs usually require an operating system to function.

Ophthalmology is the branch of medicine that deals with the anatomy, physiology and diseases of the eye. An ophthalmologist is a specialist in medical and surgical eye problems. Since ophthalmologists perform operations on eyes, they are both surgical and medical specialists. A multitude of diseases and conditions can be diagnosed from the eye.

Optical character recognition or optical character reader (OCR) is the electronic or mechanical conversion of images of typed, handwritten or printed text into machine-encoded text, whether from a scanned document, a photo of a document, a scene-photo (for example the text on signs and billboards in a landscape photo) or from subtitle text superimposed on an image (for example: from a television broadcast).

Orthotics is a specialty within the medical field concerned with the design, manufacture and application of orthoses. An orthosis (plural: orthoses) is "an externally applied device used to modify the structural and functional characteristics of the neuromuscular and skeletal system". An orthotist is the primary medical clinician responsible for the prescription, manufacture and management of orthoses.

Otorhinolaryngology (Otolaryngology) is the area of medicine that deals with disorders and conditions of the ear, nose, and throat (ENT) region, and related areas of the head and neck. Doctors who specialize in this area are called otorhinolaryngologists, otolaryngologists, ENT doctors, ENT surgeons, or head and neck surgeons. Patients seek treatment from an otorhinolaryngologist for diseases of the ear, nose, or throat and for the management of cancers of the head and neck.

An output device is any piece of computer hardware equipment used to communicate the results of data processing carried out by an information processing system (such as a computer) which converts the electronically generated information into human-readable form.

An overlay keyboard is a specialized keyboard with no pre-set keys. Each key can be programmed with a wide range of different functions. Overlay keyboards are often used as a quick and easy way to input items with just two buttons. Overlay keyboards generally consist of a flat grid of unmarked buttons. After the keyboard is programmed, a sheet, called an overlay, is placed overtop to identify each key. The overlay can consist of any combination of words, symbols, or even pictures.