Accountable Care Organization (ACO): A healthcare organization characterized by a payment and care delivery model that seeks to tie provider reimbursements to quality metrics and reductions in the total cost of care for an assigned population of patients. (Wikipedia)

Analog: A continuous signal where the time varying variable is represented by another time varying quantity. It differs from a digital signal where a continuous quantity is represented by a discrete function that only takes on one of a finite number of values.

Application Service Provider (ASP): An ASP hosts a variety of applications on a central server. For a fee, customers can access the applications over secure Internet connections or a private network. This means that they do not need to purchase, install or maintain the software themselves; instead they rent the applications they need from the ASP. New releases, such as software upgrades, are generally included in the price.

Asynchronous: Term describing store and forward transmission of medical images and/or data because the data transfer takes place over a period of time, and typically in separate time frames. The transmission typically does not take place simultaneously. This is the opposite of synchronous (see below).

Asynchronous Transfer Mode (ATM): A telecommunications standard to support voice, video and data communications. The mode uses asynchronous time-division multiplexing and encodes data into small, fixed-sized cells rather than packets or frames.

Authentication: A method of verifying the identity of a person sending or receiving information using passwords, keys and other automated identifiers.