A Drinfeld ring is the ring 
of regular
functions on 
,
where 
is a smooth geometrically connected projective algebraic curve over a finite
field 
and 
is a fixed closed
point of 
.
Here, 
is a prime power, and 
need not be 
-rational. Note that the units
of 
are the units
of 
.
As an example, let 
be the projective line 
and choose 
to be its usual point at infinity. Then ![A=F_q[T]](/images/equations/DrinfeldRing/Inline15.svg)
.
Another example is the following. Suppose that 
and let 
be given by 
with 
a separable polynomial
of even positive degree and leading coefficient nonsquare in 
. Let 
be the point above 
. Then ![A=F_q[X,Y]](/images/equations/DrinfeldRing/Inline23.svg)
.
