diff --git a/doc/reference/kernel/other/atomic.rst b/doc/reference/kernel/other/atomic.rst
index 4c792e7404d..607b4d2e8ab 100644
--- a/doc/reference/kernel/other/atomic.rst
+++ b/doc/reference/kernel/other/atomic.rst
@@ -3,8 +3,9 @@
 Atomic Services
 ###############
 
-An :dfn:`atomic variable` is a 32-bit variable that can be read and modified
-by threads and ISRs in an uninterruptible manner.
+An :dfn:`atomic variable` is one that can be read and modified
+by threads and ISRs in an uninterruptible manner. It 32-bit on
+32-bit machines and 64-bit on 64-bit machines.
 
 .. contents::
     :local: