diff --git a/src/libcore/mem.rs b/src/libcore/mem.rs
index 97b3554b1e1b..937f73a32627 100644
--- a/src/libcore/mem.rs
+++ b/src/libcore/mem.rs
@@ -88,7 +88,7 @@ pub fn align_of_val<T>(_val: &T) -> uint {
 
 /// Create a value initialized to zero.
 ///
-/// This function is similar to allocating space for a a local variable and
+/// This function is similar to allocating space for a local variable and
 /// zeroing it out (an unsafe operation).
 ///
 /// Care must be taken when using this function, if the type `T` has a
diff --git a/src/libcore/num/mod.rs b/src/libcore/num/mod.rs
index f5505ff8e762..ab9d08813854 100644
--- a/src/libcore/num/mod.rs
+++ b/src/libcore/num/mod.rs
@@ -196,7 +196,7 @@ pub trait Int
     /// ```
     fn swap_bytes(self) -> Self;
 
-    /// Convert a integer from big endian to the target's endianness.
+    /// Convert an integer from big endian to the target's endianness.
     ///
     /// On big endian this is a no-op. On little endian the bytes are swapped.
     ///
@@ -218,7 +218,7 @@ pub trait Int
         if cfg!(target_endian = "big") { x } else { x.swap_bytes() }
     }
 
-    /// Convert a integer from little endian to the target's endianness.
+    /// Convert an integer from little endian to the target's endianness.
     ///
     /// On little endian this is a no-op. On big endian the bytes are swapped.
     ///