Built-in Mathematica Symbol

NumberForm

NumberForm[expr, n]
prints with approximate real numbers in expr given to n-digit precision.

NumberForm[expr, {n, f}] prints with approximate real numbers having n digits, with f digits to the right of the decimal point.

DigitBlock	Infinity	number of digits between breaks
ExponentFunction	Automatic	function to apply to exponents
ExponentStep	1	steps by which exponents can increase
NumberFormat	Automatic	function used to assemble mantissa, base, exponent
NumberMultiplier	"×"	string to use to indicate multiplication
NumberPadding	{"","0"}	strings to use for left and right padding
NumberPoint	"."	decimal point string
NumberSeparator	{",", " "}	string to insert at breaks between blocks
NumberSigns	{"-",""}	strings to use for signs of negative and positive numbers
SignPadding	False	whether to insert padding after the sign

All options except ExponentFunction and ExponentStep apply to integers as well as approximate real numbers.

Display the first 10 digits of a numeric approximation to

:

Out[1]//NumberForm=

Display a number with 3 precise digits and 4 digits to the right of the decimal:

Out[1]//NumberForm=