Index cards in a rolodex, an old library card catalog or other organizational purpose, usually but not always 3" x 5", early and mid-20th century technologies for maintaining list of information, and in the card catalog also useful for cross-referencing information
The Index (journal), a European propaganda journal created by Henry Hotze to support the Confederate States of America during the American Civil War or, a European informational journal supporting the rebellion against the United States of America during the War Between the States.
Thumb index, a round cut-out in the pages of a publication
Diversity index – a quantitative measure that increases when the number of types (distinct groups) into which a set of entities (a population) has been classified increases, and obtains its maximum value for a given number of types when all types are represented proportional to their number within the set of entities
Lookup table, a data structure, usually an array or associative array, often used to replace a runtime computation with a simpler array indexing operation
Array index, an integer pointer (into an array data structure) that identifies an element of the array
Indexicality, the variation of meaning of an utterance according to certain features of the context in which it is uttered
A number or other symbol that indicates the location of a variable in an indexed family or set such as a list or array of numbers or other mathematical objects, usually written as a subscript to the variable; e.g. in the list , the number is the index of the third element, .
A numerical value attached to a mathematical object, such as those listed here under Algebra and Analysis
The index of summationi is used to calculate a sum, e.g.: