diff --git a/src/include/R_ext/Arith.h b/src/include/R_ext/Arith.h
index 0a5a852be56..d1b9cec6bf7 100644
--- a/src/include/R_ext/Arith.h
+++ b/src/include/R_ext/Arith.h
@@ -22,7 +22,7 @@
  *  https://www.R-project.org/Licenses/
  */
 
-/* Included by R.h: API */
+/* Included by R.h: Part of the API. */
 
 #ifndef R_ARITH_H_
 #define R_ARITH_H_
diff --git a/src/include/R_ext/BLAS.h b/src/include/R_ext/BLAS.h
index e7f125fb04e..2c6f636fba4 100644
--- a/src/include/R_ext/BLAS.h
+++ b/src/include/R_ext/BLAS.h
@@ -30,8 +30,6 @@
    $(BLAS_LIBS) $(FLIBS)
  */
 
-/* Part of the API */
-
 #ifndef R_BLAS_H
 #define R_BLAS_H
 
diff --git a/src/include/R_ext/Boolean.h b/src/include/R_ext/Boolean.h
index 56bce4e4a0b..9d643aa3b02 100644
--- a/src/include/R_ext/Boolean.h
+++ b/src/include/R_ext/Boolean.h
@@ -21,7 +21,7 @@
  *  https://www.R-project.org/Licenses/
  */
 
-/* Included by R.h: API */
+/* Included by R.h: Part of the API. */
 
 #ifndef R_EXT_BOOLEAN_H_
 #define R_EXT_BOOLEAN_H_
diff --git a/src/include/R_ext/Complex.h b/src/include/R_ext/Complex.h
index b18115f5f4d..6d27ac70072 100644
--- a/src/include/R_ext/Complex.h
+++ b/src/include/R_ext/Complex.h
@@ -21,7 +21,7 @@
  *  https://www.R-project.org/Licenses/
  */
 
-/* Included by R.h: API */
+/* Included by R.h: Part of the API. */
 
 #ifndef R_COMPLEX_H
 #define R_COMPLEX_H
diff --git a/src/include/R_ext/Constants.h b/src/include/R_ext/Constants.h
index d7b326b88fd..ad7c1247776 100644
--- a/src/include/R_ext/Constants.h
+++ b/src/include/R_ext/Constants.h
@@ -22,7 +22,7 @@
  *  https://www.R-project.org/Licenses/
  */
 
-/* Included by R.h: API */
+/* Included by R.h: Part of the API. */
 
 #ifndef R_EXT_CONSTANTS_H_
 #define R_EXT_CONSTANTS_H_
diff --git a/src/include/R_ext/Error.h b/src/include/R_ext/Error.h
index 91a535337e4..5bccb3d7103 100644
--- a/src/include/R_ext/Error.h
+++ b/src/include/R_ext/Error.h
@@ -21,7 +21,7 @@
  *  https://www.R-project.org/Licenses/
  */
 
-/* Included by R.h: API */
+/* Included by R.h: Part of the API. */
 
 #ifndef R_ERROR_H_
 #define R_ERROR_H_
diff --git a/src/include/R_ext/Memory.h b/src/include/R_ext/Memory.h
index a63d9be971b..05fde59ee5c 100644
--- a/src/include/R_ext/Memory.h
+++ b/src/include/R_ext/Memory.h
@@ -24,7 +24,7 @@
  * Memory Allocation (garbage collected) --- INCLUDING S compatibility ---
  */
 
-/* Included by R.h: API */
+/* Included by R.h: Part of the API. */
 
 #ifndef R_EXT_MEMORY_H_
 #define R_EXT_MEMORY_H_
diff --git a/src/include/R_ext/Print.h b/src/include/R_ext/Print.h
index ff6a3d95b39..1888b6faa87 100644
--- a/src/include/R_ext/Print.h
+++ b/src/include/R_ext/Print.h
@@ -21,7 +21,7 @@
  *  https://www.R-project.org/Licenses/
  */
 
-/* Included by R.h: API */
+/* Included by R.h: Part of the API. */
 
 #ifndef R_EXT_PRINT_H_
 #define R_EXT_PRINT_H_
diff --git a/src/include/R_ext/Random.h b/src/include/R_ext/Random.h
index 7dc13f9b9ee..64d5c0f9121 100644
--- a/src/include/R_ext/Random.h
+++ b/src/include/R_ext/Random.h
@@ -21,7 +21,7 @@
  *  https://www.R-project.org/Licenses/
  */
 
-/* Included by R.h: API */
+/* Included by R.h: Part of the API. */
 
 #ifndef R_RANDOM_H
 #define R_RANDOM_H
diff --git a/src/include/R_ext/Utils.h b/src/include/R_ext/Utils.h
index 95afb645d4a..69d40adce7a 100644
--- a/src/include/R_ext/Utils.h
+++ b/src/include/R_ext/Utils.h
@@ -120,7 +120,7 @@ int F77_SUB(interv)(double *xt, int *n, double *x,
 		    Rboolean *rightmost_closed, Rboolean *all_inside,
 		    int *ilo, int *mflag);
 #endif
-/* not API, mo longer in R
+/* not API, no longer in R
 void find_interv_vec(double *xt, int *n,	double *x,   int *nx,
 		     int *rightmost_closed, int *all_inside, int *indx);
 */