Improve wording on alignof and sizeof pages

docs/syntax_and_semantics/alignof.md

@@ -25,12 +25,12 @@ alignof(Bar) # => 1
 For [Reference](https://crystal-lang.org/api/Reference.html) types, the alignment is the same as the alignment of a pointer:
 
 ```crystal
-# On a 64 bits machine
+# On a 64-bit machine
 alignof(Pointer(Int32)) # => 8
 alignof(String)         # => 8
 ```
 
-This is because a Reference's memory is allocated on the heap and a pointer to it is passed around. To get the effective alignment of a class, use [instance_alignof](instance_alignof.md).
+This is because a reference's memory is allocated on the heap and a pointer to it is passed around. To get the effective alignment of a class, use [instance_alignof](instance_alignof.md).
 
 The argument to alignof is a [type](type_grammar.md) and is often combined with [typeof](typeof.md):
 

docs/syntax_and_semantics/instance_alignof.md

@@ -1,6 +1,8 @@
 # instance_alignof
 
-The `instance_alignof` expression returns an `Int32` with the instance alignment of a given class. For example:
+The `instance_alignof` expression returns an `Int32` with the instance alignment of a given class. 
+It's the equivalent to [`alignof`](alignof.md) but for reference types.
+For example:
 
 ```crystal
 class Foo

docs/syntax_and_semantics/instance_sizeof.md

@@ -1,6 +1,8 @@
 # instance_sizeof
 
-The `instance_sizeof` expression returns an `Int32` with the instance size of a given class. For example:
+The `instance_sizeof` expression returns an `Int32` with the instance size of a given class.
+It's the equivalent to [`sizeof`](sizeof.md) but for reference types.
+For example:
 
 ```crystal
 class Point

docs/syntax_and_semantics/sizeof.md

@@ -10,12 +10,12 @@ sizeof(Int64) # => 8
 For [Reference](https://crystal-lang.org/api/Reference.html) types, the size is the same as the size of a pointer:
 
 ```crystal
-# On a 64 bits machine
+# On a 64-bit machine
 sizeof(Pointer(Int32)) # => 8
 sizeof(String)         # => 8
 ```
 
-This is because a Reference's memory is allocated on the heap and a pointer to it is passed around. To get the effective size of a class, use [instance_sizeof](instance_sizeof.md).
+This is because a reference's memory is allocated on the heap and a pointer to it is passed around. To get the effective size of a class, use [instance_sizeof](instance_sizeof.md).
 
 The argument to sizeof is a [type](type_grammar.md) and is often combined with [typeof](typeof.md):