diff --git a/components/locale_core/src/extensions/unicode/attributes.rs b/components/locale_core/src/extensions/unicode/attributes.rs
index 357ae8a2667..53152bbbc29 100644
--- a/components/locale_core/src/extensions/unicode/attributes.rs
+++ b/components/locale_core/src/extensions/unicode/attributes.rs
@@ -148,6 +148,29 @@ impl Attributes {
     {
         self.deref().iter().map(|t| t.as_str()).try_for_each(f)
     }
+
+    /// Extends the `Attributes` with values from another `Attributes`.
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// use icu::locale::extensions::unicode::Attributes;
+    ///
+    /// let mut attrs: Attributes = "foobar-foobaz".parse().unwrap();
+    /// let attrs2: Attributes = "foobar-fooqux".parse().unwrap();
+    ///
+    /// attrs.extend(attrs2);
+    ///
+    /// assert_eq!(attrs, "foobar-foobaz-fooqux".parse().unwrap());
+    /// ```
+    #[cfg(feature = "alloc")]
+    pub fn extend(&mut self, other: Attributes) {
+        for attr in other.0 {
+            if let Err(idx) = self.binary_search(&attr) {
+                self.0.insert(idx, attr);
+            }
+        }
+    }
 }
 
 /// ✨ *Enabled with the `alloc` Cargo feature.*
diff --git a/components/locale_core/src/extensions/unicode/keywords.rs b/components/locale_core/src/extensions/unicode/keywords.rs
index f3ecd4cad72..c31921a318b 100644
--- a/components/locale_core/src/extensions/unicode/keywords.rs
+++ b/components/locale_core/src/extensions/unicode/keywords.rs
@@ -386,6 +386,27 @@ impl Keywords {
         Ok(())
     }
 
+    /// Extends the `Keywords` with values from  another `Keywords`.
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// use icu::locale::extensions::unicode::Keywords;
+    ///
+    /// let mut kw: Keywords = "ab-cd-ca-buddhist".parse().unwrap();
+    /// let kw2: Keywords = "ca-gregory-hc-h12".parse().unwrap();
+    ///
+    /// kw.extend(kw2);
+    ///
+    /// assert_eq!(kw, "ab-cd-ca-gregory-hc-h12".parse().unwrap());
+    /// ```
+    #[cfg(feature = "alloc")]
+    pub fn extend(&mut self, other: Keywords) {
+        for (key, value) in other.0 {
+            self.0.insert(key, value);
+        }
+    }
+
     /// This needs to be its own method to help with type inference in helpers.rs
     #[cfg(test)]
     pub(crate) fn from_tuple_vec(v: Vec<(Key, Value)>) -> Self {
diff --git a/components/locale_core/src/extensions/unicode/mod.rs b/components/locale_core/src/extensions/unicode/mod.rs
index 9577d397df3..0b60f779f6d 100644
--- a/components/locale_core/src/extensions/unicode/mod.rs
+++ b/components/locale_core/src/extensions/unicode/mod.rs
@@ -214,6 +214,26 @@ impl Unicode {
         }
         Ok(())
     }
+
+    /// Extends the `Unicode` with values from  another `Unicode`.
+    ///
+    /// # Example
+    ///
+    /// ```
+    /// use icu::locale::extensions::unicode::Unicode;
+    ///
+    /// let mut ue: Unicode = "u-foobar-ca-buddhist".parse().unwrap();
+    /// let ue2: Unicode = "u-ca-gregory-hc-h12".parse().unwrap();
+    ///
+    /// ue.extend(ue2);
+    ///
+    /// assert_eq!(ue, "u-foobar-ca-gregory-hc-h12".parse().unwrap());
+    /// ```
+    #[cfg(feature = "alloc")]
+    pub fn extend(&mut self, other: Unicode) {
+        self.keywords.extend(other.keywords);
+        self.attributes.extend(other.attributes);
+    }
 }
 
 /// ✨ *Enabled with the `alloc` Cargo feature.*
diff --git a/components/locale_core/src/preferences/mod.rs b/components/locale_core/src/preferences/mod.rs
index fe47b1e2b6f..e74ffb04362 100644
--- a/components/locale_core/src/preferences/mod.rs
+++ b/components/locale_core/src/preferences/mod.rs
@@ -37,7 +37,7 @@
 //!
 //! # Preferences Merging
 //!
-//! In traditional internatonalization APIs, the argument passed to constructors is a locale.
+//! In traditional internationalization APIs, the argument passed to constructors is a locale.
 //! ICU4X changes this paradigm by accepting a `Preferences`, which can be extracted from a [`Locale`] and combined with
 //! other `Preferences`s provided by the environment.
 //!