Character represents a single character in Read.

Context[] gives the current context. Context[symbol] gives the context in which a symbol appears.

Contexts[] gives a list of all contexts. Contexts["string"] gives a list of the contexts that match the string.

Expression is a symbol that represents an ordinary Mathematica expression in Read and related functions.

FileByteCount["file"] gives the number of bytes in a file.

FileType["file"] gives the type of a file, typically File, Directory, or None.

GeneratedCell is an option for Cell that indicates whether the cell was generated from the kernel.

NameQ["string"] yields True if there are any symbols whose names match the string pattern given, and yields False otherwise.

Setting[expr] replaces control objects such as sliders or popup menus in expr by their settings.

Word represents a word in Read, Find, and related functions.