diff --git a/mlir/docs/Traits.md b/mlir/docs/Traits.md
--- a/mlir/docs/Traits.md
+++ b/mlir/docs/Traits.md
@@ -249,7 +249,7 @@
 -   Ops must be symbols, i.e. also have the `Symbol` trait;
 -   Ops have a single region with multiple blocks that corresponds to the body
     of the function;
--   the absence of a region corresponds to an external function;
+-   An op with a single empty region corresponds to an external function;
 -   arguments of the first block of the region are treated as function
     arguments;
 -   they can have argument and result attributes that are stored in dictionary
diff --git a/mlir/include/mlir/IR/FunctionSupport.h b/mlir/include/mlir/IR/FunctionSupport.h
--- a/mlir/include/mlir/IR/FunctionSupport.h
+++ b/mlir/include/mlir/IR/FunctionSupport.h
@@ -79,7 +79,7 @@
 /// - Ops must be symbols, i.e. also have the `Symbol` trait;
 /// - Ops have a single region with multiple blocks that corresponds to the body
 ///   of the function;
-/// - the absence of a region corresponds to an external function;
+/// - An op with a single empty region corresponds to an external function;
 /// - leading arguments of the first block of the region are treated as function
 ///   arguments;
 /// - they can have argument attributes that are stored in a dictionary