Arrow (symbol) in the context of Billboards

A cross-reference (sometimes abbreviated as xref) is an instance within a document which refers the reader to related or synonymous information elsewhere, usually within the same work. To cross-reference is to make such connections. Cross-references typically link to a related topic. Cross-referencing is usually employed by readers to either verify claims made by an author or to find information on a topic of interest. In both printed and online dictionaries cross-references are important because they form a network structure of relations existing between different parts of data, dictionary-internal as well as dictionary external.

Print reference works, such as dictionaries and encyclopedias, have used various typographical elements such as bold text, small caps, or italics; symbols such as the manicule or arrow; and the words see also or for to indicate terms that can be cross-referenced. For example, under the term Albert Einstein in the index of a book about Nobel Laureates, there may be the cross-reference See Also: Einstein, Albert. Cross-references and marginal notes in printed text served a linking function similar to what is seen in hypertext.

The arrow keys (↑ Up, ← Left, ↓ Down and → Right) are the four keys on a computer keyboard labelled with directional arrows, typically found in an inverted-T layout to the bottom-right of the keyboard and to the left of the numeric keypad. They are a subset of the cursor keys, which include others like the Home, End, and Page Up/Down keys.

The arrow keys have a wide variety of functions. In a command-line interface (CLI), text box, or word processor, they typically enable caret navigation, allowing the user to move the text cursor between characters and lines. Meanwhile, in graphical user interfaces (GUIs), file viewers, and web browsers, the keys are generally used for scrolling, providing an alternative to dragging a scrollbar with a mouse pointer. Specific kinds of software make use of the arrow keys in more unique ways: they are used in most media player software to skip backward or forward through audio and video files, and they are used in some video games to move a player character around a virtual space (although modern games typically use the WASD keys for this purpose).