diff --git a/libraries/APO/APO_DefaultSetup.h b/libraries/APO/APO_DefaultSetup.h
index 5e13201ca7..c718f3ac65 100644
--- a/libraries/APO/APO_DefaultSetup.h
+++ b/libraries/APO/APO_DefaultSetup.h
@@ -77,7 +77,7 @@ void setup() {
 		 * On detecting NULL assigned to any ultrasonic sensor, its corresponding block of code
 		 * will not be executed by the navigator.
 		 * The coordinate system is assigned by the right hand rule with the thumb pointing down.
-		 * In set_orientation, it is defind as (front/back,left/right,down,up)
+		 * In set_orientation, it is defined as (front/back,left/right,down,up)
 		 */
 
 		if (rangeFinderFrontEnabled) {
diff --git a/libraries/APO/AP_Autopilot.cpp b/libraries/APO/AP_Autopilot.cpp
index 96dab80e12..f7ed3dca1f 100644
--- a/libraries/APO/AP_Autopilot.cpp
+++ b/libraries/APO/AP_Autopilot.cpp
@@ -59,7 +59,7 @@ AP_Autopilot::AP_Autopilot(AP_Navigator * navigator, AP_Guide * guide,
 			}
 		} else if (hal->getMode() == MODE_HIL_CNTL) { // hil
 			_hal->hil->receive();
-			Serial.println("HIL Recieve Called");
+			Serial.println("HIL Receive Called");
 			if (_navigator->getTimeStamp() != 0) {
 				// give hil a chance to send some packets
 				for (int i = 0; i < 5; i++) {
diff --git a/libraries/APO/AP_Autopilot.h b/libraries/APO/AP_Autopilot.h
index ceb7be2b76..08daf19f57 100644
--- a/libraries/APO/AP_Autopilot.h
+++ b/libraries/APO/AP_Autopilot.h
@@ -42,7 +42,7 @@
 #include "AP_CommLink.h"
 
 /**
- * ArduPilotOne namespace to protect varibles
+ * ArduPilotOne namespace to protect variables
  * from overlap with avr and libraries etc.
  * ArduPilotOne does not use any global
  * variables.
@@ -58,7 +58,7 @@ class AP_CommLink;
  * as well as the hardware abstraction layer.
  *
  * It inherits from loop to manage
- * the subloops and sets the overall
+ * the sub-loops and sets the overall
  * frequency for the autopilot.
  *
 
@@ -138,7 +138,7 @@ private:
 
 	/**
 	 * Loop 4 Callbacks
-	 * - super slow mesages
+	 * - super slow messages
 	 * - log writing
 	 * @see callback0
 	 */
diff --git a/libraries/APO/template.h b/libraries/APO/template.h
index 4bed52d485..0ebf3dd191 100644
--- a/libraries/APO/template.h
+++ b/libraries/APO/template.h
@@ -21,7 +21,7 @@
 
 namespace apo {
 
-/// Class desciprtion
+/// Class description
 class Class {
 public:
 }