diff --git a/include/rtdef.h b/include/rtdef.h
index b6953d4580265c5659b7b9b421f906bf38773940..9639923bc46c76a8dee880934eb3e24bc9ef6b6c 100644
--- a/include/rtdef.h
+++ b/include/rtdef.h
@@ -67,7 +67,7 @@ typedef rt_base_t                       rt_off_t;       /**< Type for offset
 #define RT_FALSE                        0   /**< boolean fails */
 /*@}*/
 
-/* maximun value of base type */
+/* maximum value of base type */
 #define RT_UINT8_MAX                    0xff            /* Maxium number of UINT8   */
 #define RT_UINT16_MAX                   0xffff          /* Maxium number of UINT16  */
 #define RT_UINT32_MAX                   0xffffffff      /* Maxium number of UINT32  */