The quotient space
![K^__1A=K_1A/{0,[-1]}](/images/equations/ReducedWhiteheadGroup/NumberedEquation1.svg) |
of the Whitehead group 
is known as the reduced Whitehead group. Here, the element
![[-1] in K_1A](/images/equations/ReducedWhiteheadGroup/Inline2.svg)
denotes the order-2 element corresponding to the unit 
where 
is the collection of 
invertible matrices with coefficients in an associative
ring 
with unit, i.e., the collection
of all units in an associative unit
ring 
.
