11 files changed, 33 insertions, 33 deletions
diff --git a/README.md b/README.md
index 6e0cab1d7..4979ea11a 100644
--- a/README.md
+++ b/README.md
@@ -6,7 +6,7 @@ mruby is the lightweight implementation of the Ruby language complying to (part
 of) the [ISO standard][ISO-standard]. Its syntax is Ruby 2.x compatible.
 
 mruby can be linked and embedded within your application.  We provide the
-interpreter program "mruby" and the interactive mruby shell "mirb" as examples.
+interpreter program "mruby", and the interactive mruby shell "mirb" as examples.
 You can also compile Ruby programs into compiled byte code using the mruby
 compiler "mrbc".  All those tools reside in the "bin" directory.  "mrbc" is
 also able to generate compiled byte code in a C source file, see the "mrbtest"
diff --git a/doc/guides/compile.md b/doc/guides/compile.md
index ef1abf88f..7a2ff2a44 100644
--- a/doc/guides/compile.md
+++ b/doc/guides/compile.md
@@ -19,10 +19,10 @@ Optional:
 * Bison (to compile `mrbgems/mruby-compiler/core/parse.y`)
 * gperf (to compile `mrbgems/mruby-compiler/core/keywords`)
 
-Note that `bison` bundled with MacOS is too old to compile `mruby`.
+Note that `bison` bundled with macOS is too old to compile `mruby`.
 Try `brew install bison` and follow the instruction shown to update
-the `$PATH` to compile `mruby`. We also encourage to upgrade `ruby`
-on MacOS in similar manner.
+the `$PATH` to compile `mruby`. We also encourage you to upgrade `ruby`
+on macOS in similar manner.
 
 ## Build
 
@@ -52,7 +52,7 @@ All tools necessary to compile mruby can be set or modified here.
 We wish you submit a pull-request to `build_config/PLATFORM.rb`, once you
 created a new configuration for a new platform.
 
-Inside of the configuration file, the following options can be
+Inside the configuration file, the following options can be
 configured based on your environment.
 
 ### Toolchains
@@ -135,7 +135,7 @@ end
 
 C Compiler has header searcher to detect installed library.
 
-If you need a include path of header file use `search_header_path`:
+If you need an include path of header file use `search_header_path`:
 
 ```ruby
 # Searches ```iconv.h```.
@@ -311,7 +311,7 @@ conf.enable_cxx_exception
 
 #### C++ exception disabling.
 
-If your compiler does not support C++ and you want to ensure
+If your compiler does not support C++, and you want to ensure
 you don't use mrbgem written in C++, you can explicitly disable
 C++ exception, add following:
 
@@ -360,7 +360,7 @@ directory.
 
 ### Mrbtest in Cross-Compilation
 
-In cross compilation, you can run `mrbtest` on emulator if
+In cross compilation, you can run `mrbtest` on an emulator if
 you have it by changing configuration of test runner.
 
 ```ruby
diff --git a/doc/guides/debugger.md b/doc/guides/debugger.md
index bb3db7cd7..2393c20b1 100644
--- a/doc/guides/debugger.md
+++ b/doc/guides/debugger.md
@@ -114,7 +114,7 @@ b [class:]method
 The breakpoint will be ordered in serial from 1.
 The number, which was given to the deleted breakpoint, will never be given to another breakpoint again.
 
-You can give multiple breakpoints to specified the line number and method.
+You can give multiple breakpoints to the specified the line number and method.
 Be ware that breakpoint command will not check the validity of the class name and method name.
 
 You can get the current breakpoint information by the following options.
@@ -165,7 +165,7 @@ Example:
 (foo.rb:1) delete
 ```
 
-This will delete all of the breakpoints.
+This will delete all the breakpoints.
 
 ```
 (foo.rb:1) delete 1 3
@@ -192,7 +192,7 @@ Example:
 (foo.rb:1) disable
 ```
 
-Use `disable` if you would like to disable all of the breakpoints.
+Use `disable` if you would like to disable all the breakpoints.
 
 ```
 (foo.rb:1) disable 1 3
@@ -324,7 +324,7 @@ expr: expression
 
 The expression is mandatory.
 The displayed expressions will be serially ordered from 1.
-If an exception occurs, the exception information will be displayed and the debugging will be continued.
+If an exception occurs, the exception information will be displayed, and the debugging will be continued.
 
 Example:
 
diff --git a/doc/guides/gc-arena-howto.md b/doc/guides/gc-arena-howto.md
index 7c367c98a..192a10802 100644
--- a/doc/guides/gc-arena-howto.md
+++ b/doc/guides/gc-arena-howto.md
@@ -11,13 +11,13 @@ execution speed.  This is an error indicating overflow of "GC arena"
 implementing "conservative GC".
 
 GC (garbage collector) must ensure that object is "alive", in other
-words, that it is referenced by somewhere from program.  This can be
+words, that it is referenced by somewhere from the program.  This can be
 determined by checking if the object can be directly or indirectly
 referenced by root.  The local variables, global variables and
 constants etc are root.
 
 If program execution is performed inside mruby VM, there is nothing to
-worry about because GC can access all roots owned by VM.
+worry about because GC can access all roots owned by the VM.
 
 The problem arises when executing C functions.  The object referenced
 by C variable is also "alive", but mruby GC cannot aware of this, so
@@ -38,7 +38,7 @@ The biggest problem is we have no way to access to the stack area in
 portable way.  Therefore, we cannot use this method if we'd like to
 implement highly portable runtime, like mruby.
 
-So we came up with an another plan to implement "conservative GC" in mruby.
+So we came up with another plan to implement "conservative GC" in mruby.
 
 Again, the problem is when an object which was created in C function, becomes
 no longer referenced in the Ruby world, and cannot be treated as garbage.
@@ -161,7 +161,7 @@ Please note that the final `inspect` representation of entire array
 was created before the call of `mrb_gc_arena_restore()`.  Otherwise,
 required temporal object may be deleted by GC.
 
-We may have a usecase where after creating many temporal objects, we'd
+We may have an usecase where after creating many temporal objects, we'd
 like to keep some of them.  In this case, we cannot use the same idea
 in `ary_inspect()` like appending objects to existing one.
 Instead, after `mrb_gc_arena_restore()`, we must re-register the objects we
diff --git a/doc/guides/mrbconf.md b/doc/guides/mrbconf.md
index 2130d51c2..2e76464d2 100644
--- a/doc/guides/mrbconf.md
+++ b/doc/guides/mrbconf.md
@@ -165,7 +165,7 @@ largest value of required alignment.
 * Please try if `MRB_USE_LINK_TIME_RO_DATA_P` is not available.
 * The `mrb_ro_data_p()` function is implemented by the user in an arbitrary file.
 * The prototype declaration is `mrb_bool mrb_ro_data_p(const char *ptr)`.
-* Return `TRUE` if `ptr` is in read-only section, otherwise return `FALSE`.
+* Return `TRUE` if `ptr` is in the read-only section, otherwise return `FALSE`.
 
 ## Other configuration.
 
diff --git a/doc/guides/mrbgems.md b/doc/guides/mrbgems.md
index 5a6396e97..00e097f4c 100644
--- a/doc/guides/mrbgems.md
+++ b/doc/guides/mrbgems.md
@@ -52,8 +52,8 @@ For specifying commit hash to checkout use `:checksum_hash` option:
 conf.gem mgem: 'mruby-redis', checksum_hash: '3446d19fc4a3f9697b5ddbf2a904f301c42f2f4e'
 ```
 
-If there is missing dependencies, mrbgem dependencies solver will reference
-mrbgem from core or mgem-list.
+If there are missing dependencies, mrbgem dependencies solver will reference
+mrbgem from the core or mgem-list.
 
 To pull all gems from remote GIT repository on build, call ```rake -p```,
 or ```rake --pull-gems```.
@@ -80,7 +80,7 @@ end
 ```
 
 As mentioned, the GemBox uses the same conventions as `MRuby::Build`.  The GemBox
-must be saved with a `.gembox` extension inside the `mrbgems` directory to to be
+must be saved with a `.gembox` extension inside the `mrbgems` directory to be
 picked up by mruby.
 
 To use this example GemBox, we save it as `custom.gembox` inside the `mrbgems`
@@ -149,7 +149,7 @@ The mrbgems build process will use this specification to compile Object and Ruby
 files. The compilation results will be added to `lib/libmruby.a`. This file exposes
 the GEM functionality to tools like `mruby` and `mirb`.
 
-The following properties can be set inside of your `MRuby::Gem::Specification` for
+The following properties can be set inside your `MRuby::Gem::Specification` for
 information purpose:
 
 * `spec.license` or `spec.licenses` (A single license or a list of them under which this GEM is licensed)
@@ -230,7 +230,7 @@ end
 ```
 
 In case your GEM has more complex build requirements you can use
-the following options additionally inside of your GEM specification:
+the following options additionally inside your GEM specification:
 
 * `spec.cc.flags` (C compiler flags)
 * `spec.cc.defines` (C compiler defines)
@@ -245,7 +245,7 @@ the following options additionally inside of your GEM specification:
 * `spec.test_objs` (Object test files for integration into mrbtest)
 * `spec.test_preload` (Initialization files for mrbtest)
 
-You also can use `spec.mruby.cc` and `spec.mruby.linker` to add extra global parameters for compiler and linker.
+You also can use `spec.mruby.cc` and `spec.mruby.linker` to add extra global parameters for the compiler and linker.
 
 ### include_paths and dependency
 
diff --git a/doc/limitations.md b/doc/limitations.md
index ee3107297..d903d528c 100644
--- a/doc/limitations.md
+++ b/doc/limitations.md
@@ -54,7 +54,7 @@ end
 
 #### mruby [3.0.0 (2021-03-05)]
 
-No exception is raised. Instead you have to do:
+No exception is raised. Instead, you have to do:
 
 ```ruby
 begin
@@ -66,7 +66,7 @@ end
 
 ## Fiber execution can't cross C function boundary
 
-mruby's `Fiber` is implemented in a similar way to Lua's co-routine. This
+mruby's `Fiber` is implemented similarly to Lua's co-routine. This
 results in the consequence that you can't switch context within C functions.
 Only exception is `mrb_fiber_yield` at return.
 
@@ -95,7 +95,7 @@ p Liste.new "foobar"
 ## Method visibility
 
 For simplicity reasons no method visibility (public/private/protected) is
-supported. Those methods are defined but they are dummy methods.
+supported. Those methods are defined, but they are dummy methods.
 
 ```ruby
 class VisibleTest
diff --git a/doc/mruby3.md b/doc/mruby3.md
index b17f3d526..aacbbb371 100644
--- a/doc/mruby3.md
+++ b/doc/mruby3.md
@@ -76,8 +76,8 @@ to be default `mrb_value` representation. Now the default is
 ## `MRB_WORD_BOXING`
 
 Pack `mrb_value` in an `intptr_t` integer. Consumes less
-memory compared to `MRB_NO_BOXING` especially on 32 bit
-platforms. `Fixnum` size is 31 bits so some integer values
+memory compared to `MRB_NO_BOXING` especially on 32-bit
+platforms. `Fixnum` size is 31 bits, so some integer values
 does not fit in `Fixnum` integers.
 
 ## `MRB_NAN_BOXING`
@@ -117,7 +117,7 @@ Instructions that access pool[i]/syms[i] where i>255.
 * `OP_STRING16`
 * `OP_LOADSYM16`
 
-Instructions that load a 32 bit integer.
+Instructions that load a 32-bit integer.
 
 * `OP_LOADI32`
 
diff --git a/doc/opcode.md b/doc/opcode.md
index 7273ff993..3ad09919c 100644
--- a/doc/opcode.md
+++ b/doc/opcode.md
@@ -1,12 +1,12 @@
 # The new bytecode
 
-We will reimplement VM to use 8bit instruction code. By
+We will reimplement the VM to use 8bit instruction code. By
 bytecode, we mean real byte code. The whole purpose is
 reducing the memory consumption of mruby VM.
 
 # Instructions
 
-Instructions are bytes. There can be 256 instructions. Currently we
+Instructions are bytes. There can be 256 instructions. Currently, we
 have 94 instructions. Instructions can take 0 to 3 operands.
 
 ## operands
diff --git a/mrbgems/mruby-method/README.md b/mrbgems/mruby-method/README.md
index 5cb0b342a..eef414c55 100644
--- a/mrbgems/mruby-method/README.md
+++ b/mrbgems/mruby-method/README.md
@@ -1,7 +1,7 @@
 mruby-method
 ===
 
-A implementation of class **Method** and **UnboundMethod** for mruby
+An implementation of class **Method** and **UnboundMethod** for mruby
 
 ```ruby
 p Enumerable.instance_method(:find_all).source_location
diff --git a/mrbgems/mruby-sleep/README.md b/mrbgems/mruby-sleep/README.md
index 0ccc7000f..cddae7c13 100644
--- a/mrbgems/mruby-sleep/README.md
+++ b/mrbgems/mruby-sleep/README.md
@@ -4,7 +4,7 @@ mruby sleep module
 
 ## install by mrbgems
 
-- add conf.gem line to your build configuration.
+- add `conf.gem` line to your build configuration.
 
 ```ruby
 MRuby::Build.new do |conf|