diff --git a/ToDo.md b/ToDo.md
index 07db5aab..80de9d48 100644
--- a/ToDo.md
+++ b/ToDo.md
@@ -1,6 +1,6 @@
 
 - [x] copy to buffer if non-contiguous.gc
-- [x] contract contiguous dimesions.gc
+- [x] contract contiguous dimensions.gc
 
 - [ ] transpose and flatten reduce dimeinsion to last user dimension. -- almost done.
 
diff --git a/doc/api.ja.md b/doc/api.ja.md
index e55d65e4..fbe0411d 100644
--- a/doc/api.ja.md
+++ b/doc/api.ja.md
@@ -157,7 +157,7 @@ typedef struct NDF_ARG_OUT {
 
     typedef struct NA_LOOP {
         int  narg;
-        int  ndim;             // n of user dimention
+        int  ndim;             // n of user dimension
         size_t *n;             // n of elements for each dim
         na_loop_args_t *args;  // for each arg
         VALUE  option;
diff --git a/ext/numo/narray/array.c b/ext/numo/narray/array.c
index 0a8807dc..8956e506 100644
--- a/ext/numo/narray/array.c
+++ b/ext/numo/narray/array.c
@@ -560,7 +560,7 @@ na_mdai_for_struct(na_mdai_t *mdai, int ndim)
             //fputs("compati\n",stderr);
             return 1;
         }
-        // otherwise, multi-dimention
+        // otherwise, multi-dimension
         if (ndim >= mdai->capa) {
             //fprintf(stderr,"exeed capa\n");            abort();
             na_mdai_realloc(mdai,4);
diff --git a/ext/numo/narray/data.c b/ext/numo/narray/data.c
index b12532c1..1501125d 100644
--- a/ext/numo/narray/data.c
+++ b/ext/numo/narray/data.c
@@ -521,7 +521,7 @@ na_flatten_dim(VALUE self, int sd)
                 na2->stridx[i] = na1->stridx[i];
             }
         }
-        // flat dimenion == last dimension
+        // flat dimension == last dimension
         if (RTEST(na_check_ladder(self,sd))) {
             na2->stridx[sd] = na1->stridx[nd-1];
         } else {
diff --git a/ext/numo/narray/gen/spec.rb b/ext/numo/narray/gen/spec.rb
index 33f8517a..ae379556 100644
--- a/ext/numo/narray/gen/spec.rb
+++ b/ext/numo/narray/gen/spec.rb
@@ -56,7 +56,7 @@
   def_id "minlength" # for bincount
 end
 
-# Constatnts
+# Constants
 
 if is_bit
   def_const "ELEMENT_BIT_SIZE",  "INT2FIX(1)"
diff --git a/ext/numo/narray/gen/tmpl/format.c b/ext/numo/narray/gen/tmpl/format.c
index e7ef9f05..3fb4d5ef 100644
--- a/ext/numo/narray/gen/tmpl/format.c
+++ b/ext/numo/narray/gen/tmpl/format.c
@@ -44,7 +44,7 @@ static void
   Format elements into strings.
   @overload <%=name%> format
   @param [String] format
-  @return [Numo::RObject] array of formated strings.
+  @return [Numo::RObject] array of formatted strings.
 */
 static VALUE
 <%=c_func(-1)%>(int argc, VALUE *argv, VALUE self)
diff --git a/ext/numo/narray/gen/tmpl/format_to_a.c b/ext/numo/narray/gen/tmpl/format_to_a.c
index 5d8f954e..2dd3daf1 100644
--- a/ext/numo/narray/gen/tmpl/format_to_a.c
+++ b/ext/numo/narray/gen/tmpl/format_to_a.c
@@ -32,7 +32,7 @@ static void
   Format elements into strings.
   @overload <%=name%> format
   @param [String] format
-  @return [Array] array of formated strings.
+  @return [Array] array of formatted strings.
 */
 static VALUE
 <%=c_func(-1)%>(int argc, VALUE *argv, VALUE self)
diff --git a/ext/numo/narray/gen/tmpl/logseq.c b/ext/numo/narray/gen/tmpl/logseq.c
index b3e13b6f..12bfc4fd 100644
--- a/ext/numo/narray/gen/tmpl/logseq.c
+++ b/ext/numo/narray/gen/tmpl/logseq.c
@@ -47,7 +47,7 @@ static void
   Applicable classes: DFloat, SFloat, DComplex, SCopmplex.
 
   @overload logseq(beg,step,[base])
-  @param [Numeric] beg  The begining of sequence.
+  @param [Numeric] beg  The beginning of sequence.
   @param [Numeric] step  The step of sequence.
   @param [Numeric] base  The base of log space. (default=10)
   @return [Numo::<%=class_name%>] self.
diff --git a/ext/numo/narray/gen/tmpl/seq.c b/ext/numo/narray/gen/tmpl/seq.c
index 271db69a..0d8cf37e 100644
--- a/ext/numo/narray/gen/tmpl/seq.c
+++ b/ext/numo/narray/gen/tmpl/seq.c
@@ -55,7 +55,7 @@ static void
      beg+i*step
   where i is 1-dimensional index.
   @overload seq([beg,[step]])
-  @param [Numeric] beg  begining of sequence. (default=0)
+  @param [Numeric] beg  beginning of sequence. (default=0)
   @param [Numeric] step  step of sequence. (default=1)
   @return [Numo::<%=class_name%>] self.
   @example
diff --git a/ext/numo/narray/gen/tmpl_bit/format.c b/ext/numo/narray/gen/tmpl_bit/format.c
index 8770f033..6d1126c2 100644
--- a/ext/numo/narray/gen/tmpl_bit/format.c
+++ b/ext/numo/narray/gen/tmpl_bit/format.c
@@ -45,7 +45,7 @@ static void
   Format elements into strings.
   @overload <%=name%> format
   @param [String] format
-  @return [Numo::RObject] array of formated strings.
+  @return [Numo::RObject] array of formatted strings.
 */
 static VALUE
 <%=c_func(-1)%>(int argc, VALUE *argv, VALUE self)
diff --git a/ext/numo/narray/gen/tmpl_bit/format_to_a.c b/ext/numo/narray/gen/tmpl_bit/format_to_a.c
index c0740db5..6f401a74 100644
--- a/ext/numo/narray/gen/tmpl_bit/format_to_a.c
+++ b/ext/numo/narray/gen/tmpl_bit/format_to_a.c
@@ -33,7 +33,7 @@ static void
   Format elements into strings.
   @overload <%=name%> format
   @param [String] format
-  @return [Array] array of formated strings.
+  @return [Array] array of formatted strings.
 */
 static VALUE
 <%=c_func(-1)%>(int argc, VALUE *argv, VALUE self)
diff --git a/ext/numo/narray/index.c b/ext/numo/narray/index.c
index 9b19b9d5..9482a587 100644
--- a/ext/numo/narray/index.c
+++ b/ext/numo/narray/index.c
@@ -16,9 +16,9 @@
 #define cIndex numo_cInt32
 #endif
 
-// note: the memory refed by this pointer is not freed and causes memroy leak.
+// note: the memory refed by this pointer is not freed and causes memory leak.
 typedef struct {
-    size_t  n; // the number of elements of the dimesnion
+    size_t  n; // the number of elements of the dimension
     size_t  beg; // the starting point in the dimension
     ssize_t step; // the step size of the dimension
     size_t *idx; // list of indices
@@ -508,7 +508,7 @@ na_index_parse_args(VALUE args, narray_t *na, na_index_arg_t *q, int ndim)
             na_index_parse_each(v, 1, k, &q[j]);
             j++;
         }
-        // other dimention
+        // other dimension
         else {
             na_index_parse_each(v, na->shape[k], k, &q[j]);
             if (q[j].n > 1) {
@@ -864,7 +864,7 @@ check_index_count(int argc, int na_ndim, int count_new, int count_rest)
                  argc,na_ndim);
         break;
     default:
-        rb_raise(rb_eIndexError,"multiple rest-dimension is not allowd");
+        rb_raise(rb_eIndexError,"multiple rest-dimension is not allowed");
     }
     return -1;
 }
diff --git a/ext/numo/narray/ndloop.c b/ext/numo/narray/ndloop.c
index 6f0d91ac..5cb3752d 100644
--- a/ext/numo/narray/ndloop.c
+++ b/ext/numo/narray/ndloop.c
@@ -41,7 +41,7 @@ typedef struct NA_LOOP_XARGS {
 typedef struct NA_MD_LOOP {
     int  narg;
     int  nin;
-    int  ndim;                // n of total dimention
+    int  ndim;                // n of total dimension
     unsigned int copy_flag;   // set i-th bit if i-th arg is cast
     void    *ptr;             // memory for n
     na_loop_iter_t *iter_ptr; // memory for iter
@@ -1280,7 +1280,7 @@ ndloop_run(VALUE vlp)
         //}
     }
 
-    // setup objects in which resuts are stored
+    // setup objects in which results are stored
     ndfunc_set_user_loop(nf, lp);
 
     // setup buffering during loop
diff --git a/ext/numo/narray/numo/ndloop.h b/ext/numo/narray/numo/ndloop.h
index e9880261..692fbf5e 100644
--- a/ext/numo/narray/numo/ndloop.h
+++ b/ext/numo/narray/numo/ndloop.h
@@ -26,7 +26,7 @@ typedef struct NA_LOOP_ARGS {
 // pass this structure to user iterator
 typedef struct NA_LOOP {
     int  narg;
-    int  ndim;             // n of user dimention  - required for each iterator.
+    int  ndim;             // n of user dimension  - required for each iterator.
     size_t *n;             // n of elements for each dim (=shape)
     na_loop_args_t *args;  // for each arg
     VALUE  option;
diff --git a/lib/numo/narray/extra.rb b/lib/numo/narray/extra.rb
index e64084ec..29ecb4e9 100644
--- a/lib/numo/narray/extra.rb
+++ b/lib/numo/narray/extra.rb
@@ -998,7 +998,7 @@ def triu!(k=0)
       end
     end
 
-    # Return the indices for the uppler-triangle on and above the k-th diagonal.
+    # Return the indices for the upper-triangle on and above the k-th diagonal.
     def triu_indices(k=0)
       if ndim < 2
         raise NArray::ShapeError, "must be >= 2-dimensional array"
@@ -1007,7 +1007,7 @@ def triu_indices(k=0)
       NArray.triu_indices(m,n,k)
     end
 
-    # Return the indices for the uppler-triangle on and above the k-th diagonal.
+    # Return the indices for the upper-triangle on and above the k-th diagonal.
     def self.triu_indices(m,n,k=0)
       x = Numo::Int64.new(m,1).seq + k
       y = Numo::Int64.new(1,n).seq