diff --git a/README.rst b/README.rst
index 8e2a53f..004f094 100644
--- a/README.rst
+++ b/README.rst
@@ -59,7 +59,7 @@
 - ASan.
   This instruments the code with AddressSanitizer to check for memory errors.
   (This includes LeakSanitizer, with recent version of gcc and clang.)
-  (With recent version of clang, this mode also intruments the code with
+  (With recent version of clang, this mode also instruments the code with
   UndefinedSanitizer to check for undefined behaviour.)
 - ASanDbg.
   Same as ASan but slower, with debug information and better stack traces.
@@ -70,7 +70,7 @@
   Same as ASan but slower, with debug information, better stack traces and
   origin tracking.
 - Check.
-  This activates the compiler warnings that depend on optimisation and treats
+  This activates the compiler warnings that depend on optimization and treats
   all warnings as errors.
 
 Switching build modes in CMake is simple. For debug mode, enter at the command line:
@@ -103,7 +103,7 @@
 
 mbed TLS includes an elaborate test suite in *tests/* that initially requires Perl to generate the tests files (e.g. *test_suite_mpi.c*). These files are generates from a **function file** (e.g. *suites/test_suite_mpi.function*) and a **data file** (e.g. *suites/test_suite_mpi.data*). The **function file** contains the template for each test function. The **data file** contains the test cases, specified as parameters that should be pushed into a template function.
 
-For machines with a Unix shell and OpenSSL (and optionnally GnuTLS) installed, additional test scripts are available:
+For machines with a Unix shell and OpenSSL (and optionally GnuTLS) installed, additional test scripts are available:
 
 - *tests/ssl-opt.sh* runs integration tests for various TLS options (renegotiation, resumption, etc.) and tests interoperability of these options with other implementations.
 - *tests/compat.sh* tests interoperability of every ciphersuite with other implementations.