How do you categorize and/or classify Enterprise IT?

Enterprise software is often categorized by the business function that it automates - such as accounting software or sales force automation software. Similarly for industries - for example, there are enterprise systems devised for the health care industry, or for manufacturing enterprises. Naming few quickly, CRM, ERP, Product Lifecycle, Supply Chain management, Supplier Relaitonship management, Business Intelligence, Quality management.

Useful references: http://en.wikipedia.org/wiki/Enterprise_software#Types_of_enterprise_software