A closed point of a topological space 
is a point 
whose singleton set 
is a closed
set. Equivalently, the set closure of 
is 
.
In an affine scheme given by the ring spectrum of a commutative ring 
, the closed points correspond precisely to the maximal
ideals of 
(Stacks Project Authors 2026b, §10.35). For example, in the ring
spectrum of the ring of integers, the prime
ideals 
for prime numbers 
give closed points, while the zero
ideal does not. A closed point is used to specify the point at infinity in the
definition of a Drinfeld module (Poonen 2021,
p. 2).
