Text sometimes exhibits case sensitivity; that is, words can differ in meaning based on differing use of uppercase and lowercase letters. Words with capital letters do not always have the same meaning when written with lowercase letters. For example, Bill is the first name of former U.S. president William Clinton, who could sign a bill (which is a proposed law that was approved by Congress). And a Polish person can use polish to clean or shine something. In food, the Calorie, with a capital C, is sometimes used to denote 1000 calories of energy.
The opposite term of "case-sensitive" is "case-insensitive".
Use in computer systems
In computers, some examples of usually case-sensitive data are:
searching for a text string within electronic text
Some computer languages are case-sensitive for their identifiers (Java, C++, C#, C,Verilog, Ruby and XML). Others are case-insensitive (i.e., not case-sensitive), such as most BASICs (an exception being BBC BASIC), Fortran, SQL and Pascal. There are also languages, such as Haskell, Prolog and Go, in which the capitalization of an identifier encodes information about its semantics.
A text search operation could be case-sensitive or case-insensitive, depending on the system, application, or context. A case-insensitive search could be more convenient, not requiring the user to provide the precise casing, and returning more results, while a case-sensitive search enables the user to focus more precisely on a narrower result set. For example, Google searches are generally case-insensitive. In Oracle SQL most operations and searches are case-sensitive by default, while in most other DBMS's SQL searches are case-insensitive by default. In most Internet browsers, the "Find in this page" feature has an option enabling the user to choose whether the search would be case-sensitive or not.