diff --git a/src/newgrf_debug_gui.cpp b/src/newgrf_debug_gui.cpp
index 3359f796fd..b96ecbd7f8 100644
--- a/src/newgrf_debug_gui.cpp
+++ b/src/newgrf_debug_gui.cpp
@@ -520,7 +520,7 @@ void DeleteNewGRFInspectWindow(GrfSpecFeature feature, uint index)
 
 	/* Reinitialise the land information window to remove the "debug" sprite if needed.
 	 * Note: Since we might be called from a command here, it is important to not execute
-	 * the invalidation immediatelly. The landinfo window tests commands itself. */
+	 * the invalidation immediately. The landinfo window tests commands itself. */
 	InvalidateWindowData(WC_LAND_INFO, 0, 1);
 }
 
diff --git a/src/train_cmd.cpp b/src/train_cmd.cpp
index e8beb46a61..e234c9d28c 100644
--- a/src/train_cmd.cpp
+++ b/src/train_cmd.cpp
@@ -264,7 +264,7 @@ void Train::ConsistChanged(bool same_length)
 	if (this->IsFrontEngine()) {
 		this->UpdateAcceleration();
 		SetWindowDirty(WC_VEHICLE_DETAILS, this->index);
-		InvalidateWindowData(WC_VEHICLE_REFIT, this->index); // Important, do not invalidate immediatelly. The refit window tests commands.
+		InvalidateWindowData(WC_VEHICLE_REFIT, this->index); // Important, do not invalidate immediately. The refit window tests commands.
 	}
 }
 
@@ -1089,7 +1089,7 @@ static void NormaliseTrainHead(Train *head)
 	if (!head->IsFrontEngine()) return;
 
 	/* Update the refit button and window */
-	InvalidateWindowData(WC_VEHICLE_REFIT, head->index); // Important, do not invalidate immediatelly. The refit window tests commands.
+	InvalidateWindowData(WC_VEHICLE_REFIT, head->index); // Important, do not invalidate immediately. The refit window tests commands.
 	SetWindowWidgetDirty(WC_VEHICLE_VIEW, head->index, VVW_WIDGET_REFIT_VEH);
 
 	/* If we don't have a unit number yet, set one. */
diff --git a/src/vehicle_gui.cpp b/src/vehicle_gui.cpp
index 61ef82ef53..6efbecf533 100644
--- a/src/vehicle_gui.cpp
+++ b/src/vehicle_gui.cpp
@@ -1120,7 +1120,7 @@ static inline void ChangeVehicleWindow(WindowClass window_class, VehicleID from_
 			_thd.window_number = to_index;
 		}
 
-		/* Notify the window immediatelly, without scheduling. */
+		/* Notify the window immediately, without scheduling. */
 		w->InvalidateData();
 	}
 }
diff --git a/src/window.cpp b/src/window.cpp
index ac4c76b3ba..57c753c52c 100644
--- a/src/window.cpp
+++ b/src/window.cpp
@@ -2477,19 +2477,19 @@ void SetWindowClassesDirty(WindowClass cls)
 
 /**
  * Mark window data of the window of a given class and specific window number as invalid (in need of re-computing)
- * Note that by default the invalidation is not executed immediatelly but is scheduled till the next redraw.
+ * Note that by default the invalidation is not executed immediately but is scheduled till the next redraw.
  * The asynchronous execution is important to prevent GUI code being executed from command scope.
  * @param cls Window class
  * @param number Window number within the class
  * @param data The data to invalidate with
- * @param immediatelly If true then do not schedule the event, but execute immediatelly.
+ * @param immediately If true then do not schedule the event, but execute immediately.
  */
-void InvalidateWindowData(WindowClass cls, WindowNumber number, int data, bool immediatelly)
+void InvalidateWindowData(WindowClass cls, WindowNumber number, int data, bool immediately)
 {
 	Window *w;
 	FOR_ALL_WINDOWS_FROM_BACK(w) {
 		if (w->window_class == cls && w->window_number == number) {
-			if (immediatelly) {
+			if (immediately) {
 				w->InvalidateData(data);
 			} else {
 				w->ScheduleInvalidateData(data);
@@ -2500,19 +2500,19 @@ void InvalidateWindowData(WindowClass cls, WindowNumber number, int data, bool i
 
 /**
  * Mark window data of all windows of a given class as invalid (in need of re-computing)
- * Note that by default the invalidation is not executed immediatelly but is scheduled till the next redraw.
+ * Note that by default the invalidation is not executed immediately but is scheduled till the next redraw.
  * The asynchronous execution is important to prevent GUI code being executed from command scope.
  * @param cls Window class
  * @param data The data to invalidate with
- * @param immediatelly If true then do not schedule the event, but execute immediatelly.
+ * @param immediately If true then do not schedule the event, but execute immediately.
  */
-void InvalidateWindowClassesData(WindowClass cls, int data, bool immediatelly)
+void InvalidateWindowClassesData(WindowClass cls, int data, bool immediately)
 {
 	Window *w;
 
 	FOR_ALL_WINDOWS_FROM_BACK(w) {
 		if (w->window_class == cls) {
-			if (immediatelly) {
+			if (immediately) {
 				w->InvalidateData(data);
 			} else {
 				w->ScheduleInvalidateData(data);
diff --git a/src/window_func.h b/src/window_func.h
index 933d198773..43f50111d4 100644
--- a/src/window_func.h
+++ b/src/window_func.h
@@ -34,8 +34,8 @@ void ResetWindowSystem();
 void SetupColoursAndInitialWindow();
 void InputLoop();
 
-void InvalidateWindowData(WindowClass cls, WindowNumber number, int data = 0, bool immediatelly = false);
-void InvalidateWindowClassesData(WindowClass cls, int data = 0, bool immediatelly = false);
+void InvalidateWindowData(WindowClass cls, WindowNumber number, int data = 0, bool immediately = false);
+void InvalidateWindowClassesData(WindowClass cls, int data = 0, bool immediately = false);
 
 void DeleteNonVitalWindows();
 void DeleteAllNonVitalWindows();