1. <software> A designer's or developer's suite of software that helps programmers isolate the {business logic} in their programs from the platform-related code. Application servers can handle all of the application logic and connectivity found in client-server applications. Many application servers also offer features such as transaction management, clustering and failover, and load balancing; nearly all offer ODBC support. Application servers range from small footprint, web-based processors for intelligent appliances or remote embedded devices, to complete environments for assembling, deploying, and maintaining scalable multi-tier applications across an enterprise. 2. <software> Production programs run on a mid-sized computer that handle all application operations between browser-based computers and an organisation's back-end business applications or databases. The application server works as a translator, allowing, for example, a customer with a browser to search an online retailer's database for pricing information. 3. <hardware> The device on which application server software runs. Application Service Providers offer commercial access to such devices. {Citrix Application Serving White Paper (http://citrix.com/press/corpinfo/application_serving_wp_0700.pdf)}. {Application Server Sites, a list maintained by Vayda & Herzum (http://componentfactory.org/links/appl.htm)}. {The Application Server Zone at DevX, (http://appserver-zone.com/default.asp)}. {TechMetrix Research's Application Server Directory, (http://techmetrix.com/trendmarkers/techmetrixasd.php3)}. (2001-03-30)

An application server is a server that hosts applications or software that delivers a business application through a communication protocol.

In computing, a server is a piece of computer hardware or software (computer program) that provides functionality for other programs or devices, called "clients". This architecture is called the client–server model.