diff --git a/lcl/include/bitmap.inc b/lcl/include/bitmap.inc
index a87b8c2dbe..cf614ecfd3 100644
--- a/lcl/include/bitmap.inc
+++ b/lcl/include/bitmap.inc
@@ -179,7 +179,7 @@ begin
   //   clNone: load image opaque (*)
   //   otherwise: use TransparentColor as transparent color
   //
-  //   (*) these are Lazarus extentions
+  //   (*) these are Lazarus extensions
 
   if (TransparentMode = tmAuto) or (TransparentColor = clDefault)
   then begin
diff --git a/lcl/include/font.inc b/lcl/include/font.inc
index 27c27a5ca9..451d96cce7 100644
--- a/lcl/include/font.inc
+++ b/lcl/include/font.inc
@@ -349,7 +349,7 @@ begin
   // ToDO: NORMAL, CONDENSED, NARROW, WIDE, EXPANDED
 
   GetNextItem; // 7. read AddStyleName
-  // calculate Style name extentions (=rotation)
+  // calculate Style name extensions (=rotation)
   //        API                 XLFD
   // --------------------- --------------
   // Orientation 1/10 deg  1/64 deg
diff --git a/lcl/interfaces/gtk/gtkwinapi.inc b/lcl/interfaces/gtk/gtkwinapi.inc
index 85f8808e5f..2274932f8e 100644
--- a/lcl/interfaces/gtk/gtkwinapi.inc
+++ b/lcl/interfaces/gtk/gtkwinapi.inc
@@ -1672,7 +1672,7 @@ begin
       // SetWidthName := '*';
       {$IFDEF OLD_ROTATION}
       if AddStyleName='*' then begin
-        // calculate Style name extentions (=rotation)
+        // calculate Style name extensions (=rotation)
         //        API                 XLFD
         // --------------------- --------------
         // Orientation 1/10 deg  1/64 deg
diff --git a/lcl/intfgraphics.pas b/lcl/intfgraphics.pas
index 3618800454..9dfe19e100 100644
--- a/lcl/intfgraphics.pas
+++ b/lcl/intfgraphics.pas
@@ -349,7 +349,7 @@ type
   
   
   { ILazImageReader }
-  { Extention to TFPCustomImageReader to initialize a TRawImgeDescription based
+  { Extension to TFPCustomImageReader to initialize a TRawImgeDescription based
     on the image to be read
   }
   
@@ -362,7 +362,7 @@ type
   end;
 
   { ILazImageWriter }
-  { Extention to TFPCustomImageWriter to initialize the writer based
+  { Extension to TFPCustomImageWriter to initialize the writer based
     on the intfimage data. To be able to write different formats, the writer
     should initialize itself
   }