diff --git a/library/alloc/src/collections/btree/map.rs b/library/alloc/src/collections/btree/map.rs
index 62153efbb39..794b9356e7c 100644
--- a/library/alloc/src/collections/btree/map.rs
+++ b/library/alloc/src/collections/btree/map.rs
@@ -34,7 +34,7 @@
 // An empty map is represented either by the absence of a root node or by a
 // root node that is an empty leaf.
 
-/// A map based on a [B-Tree].
+/// An ordered map based on a [B-Tree].
 ///
 /// B-Trees represent a fundamental compromise between cache-efficiency and actually minimizing
 /// the amount of work performed in a search. In theory, a binary search tree (BST) is the optimal
@@ -68,6 +68,10 @@
 /// incorrect results, aborts, memory leaks, or non-termination) but will not be undefined
 /// behavior.
 ///
+/// Iterators obtained from functions such as [`BTreeMap::iter`], [`BTreeMap::values`], or
+/// [`BTreeMap::keys`] produce their items in order by key, and take worst-case logarithmic and
+/// amortized constant time per item returned.
+///
 /// [B-Tree]: https://en.wikipedia.org/wiki/B-tree
 /// [`Cell`]: core::cell::Cell
 /// [`RefCell`]: core::cell::RefCell
diff --git a/library/alloc/src/collections/btree/set.rs b/library/alloc/src/collections/btree/set.rs
index 394c21bf51c..31df4e98ed7 100644
--- a/library/alloc/src/collections/btree/set.rs
+++ b/library/alloc/src/collections/btree/set.rs
@@ -15,7 +15,7 @@
 
 // FIXME(conventions): implement bounded iterators
 
-/// A set based on a B-Tree.
+/// An ordered set based on a B-Tree.
 ///
 /// See [`BTreeMap`]'s documentation for a detailed discussion of this collection's performance
 /// benefits and drawbacks.
@@ -27,6 +27,9 @@
 /// incorrect results, aborts, memory leaks, or non-termination) but will not be undefined
 /// behavior.
 ///
+/// Iterators returned by [`BTreeSet::iter`] produce their items in order, and take worst-case
+/// logarithmic and amortized constant time per item returned.
+///
 /// [`Ord`]: core::cmp::Ord
 /// [`Cell`]: core::cell::Cell
 /// [`RefCell`]: core::cell::RefCell
diff --git a/library/alloc/src/collections/mod.rs b/library/alloc/src/collections/mod.rs
index 1ea135a2aed..628a5b15567 100644
--- a/library/alloc/src/collections/mod.rs
+++ b/library/alloc/src/collections/mod.rs
@@ -14,7 +14,7 @@
 #[cfg(not(no_global_oom_handling))]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub mod btree_map {
-    //! A map based on a B-Tree.
+    //! An ordered map based on a B-Tree.
     #[stable(feature = "rust1", since = "1.0.0")]
     pub use super::btree::map::*;
 }
@@ -22,7 +22,7 @@ pub mod btree_map {
 #[cfg(not(no_global_oom_handling))]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub mod btree_set {
-    //! A set based on a B-Tree.
+    //! An ordered set based on a B-Tree.
     #[stable(feature = "rust1", since = "1.0.0")]
     pub use super::btree::set::*;
 }