DigitCharacter represents a digit character 0\[Dash]9 in StringExpression.
DigitQ
(Built-in Mathematica Symbol) DigitQ[string] yields True if all the characters in the string are digits in the range 0 through 9, and yields False otherwise.
Environment["var"] gives the value of an operating system environment variable.
EuclideanDistance[u, v] gives the Euclidean distance between vectors u and v.
FilePrint["file"] prints out the raw textual contents of file.
FontVariations is an option for Style, Cell, and related constructs that specifies what font variations should be used.
FrameStyle is an option for Graphics, Grid, and other constructs that specifies the style in which to draw frames.
IntervalMemberQ[interval, x] gives True if the number x lies within the specified interval, and False otherwise. IntervalMemberQ[interval_1, interval_2] gives True if ...
NumberString represents the characters of a number in StringExpression.
PageBreakAbove is an option for Cell which specifies whether a page break should be made immediately above the cell if the notebook that contains the cell is printed.