diff --git a/src/lib.rs b/src/lib.rs
index d5a5b99..da73d88 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -372,6 +372,9 @@ impl Debug for SourceFile {
 }
 
 /// A region of source code, along with macro expansion information.
+///
+/// A Span is semi-open: the start location is included in the span and
+/// the end is excluded.
 #[derive(Copy, Clone)]
 pub struct Span {
     inner: imp::Span,
@@ -478,6 +481,9 @@ impl Span {
 
     /// Get the ending line/column in the source file for this span.
     ///
+    /// The ending line/column is exclusive, pointing to the first character
+    /// after the span.
+    ///
     /// This method requires the `"span-locations"` feature to be enabled.
     ///
     /// When executing in a procedural macro context, the returned line/column