FractionLine is an option for fractions that specifies the thickness of the line separating the numerator and denominator.
GridDefaultElement is an option for the low-level function GridBox that specifies what to insert when a new element is created interactively in a GridBox.
LetterCharacter represents a letter character in StringExpression.
LibraryFunctionError[name, code] represents an error returned from a LibraryFunction.
NullRecords is an option for Read and related functions which specifies whether null records should be taken to exist between repeated record separators.
PasteButton[expr] represents a button that pastes expr whenever it is pressed. PasteButton[label, expr] displays with label on the button.
PowerModList[a, s/r, m] gives a list of all x modulo m for which x^r \[Congruent] a^s mod m.
ScreenRectangle is a global option that specifies the position of the screen by giving the coordinates of two diagonally opposite corners.
SelectionAnimate[notebook] animates graphics in the current selection in a notebook. SelectionAnimate[notebook, t] animates graphics for t seconds.
StartOfLine represents the start of a line in a string for purposes of matching in StringExpression.