The term "atom" refers to an expression or statement which represents an indivisible structure that cannot be broken down into smaller parts or elements.
In specific areas of mathematics, "atom" may refer to:
1. In set theory, an urelement,
2. In mathematical logic, an atomic statement, or
3. In a partially ordered set with a least element 
, an element 
for which there is no element 
with 
.
In a Boolean algebra, these are its minimal nonzero elements.
