Uninstall (Built-in Mathematica Symbol)

Uninstall[link] terminates an external program started by Install, and removes Mathematica definitions set up by it.

Unique (Built-in Mathematica Symbol)

Unique[] generates a new symbol, whose name is of the form $nnn. Unique[x] generates a new symbol, with a name of the form x$nnn. Unique[{x, y, ...}] generates a list of new ...

Unitize (Built-in Mathematica Symbol)

Unitize[x] gives 0 when x is zero, and 1 when x has any other numerical value.

UnsameQ (Built-in Mathematica Symbol)

lhs =!= rhs yields True if the expression lhs is not identical to rhs, and yields False otherwise.

Unset (Built-in Mathematica Symbol)

lhs =. removes any rules defined for lhs.

Update (Built-in Mathematica Symbol)

Update[symbol] tells Mathematica that hidden changes have been made which could affect values associated with a symbol. Update[] specifies that the value of any symbol could ...

UpSet (Built-in Mathematica Symbol)

lhs ^= rhs assigns rhs to be the value of lhs, and associates the assignment with symbols that occur at level one in lhs.

ValueQ (Built-in Mathematica Symbol)

ValueQ[expr] gives True if a value has been defined for expr, and gives False otherwise.

Variables (Built-in Mathematica Symbol)

Variables[poly] gives a list of all independent variables in a polynomial.

Verbatim (Built-in Mathematica Symbol)

Verbatim[expr] represents expr in pattern matching, requiring that expr be matched exactly as it appears, with no substitutions for blanks or other transformations.