types+grammar: ch1, QC1 edits

types & grammar/ch1.md

@@ -78,7 +78,7 @@ var a = null;
 (!a && typeof a === "object"); // true
 ```
 
-`null` is the only value that is "falsy" (aka false-like; see Chapter 4) but that also returns `"object"` from the `typeof` check.
+`null` is the only primitive value that is "falsy" (aka false-like; see Chapter 4) but that also returns `"object"` from the `typeof` check.
 
 So what's the seventh string value that `typeof` can return?
 
@@ -104,7 +104,7 @@ a.length; // 2
 
 Since you declared the function with two formal named parameters (`b` and `c`), the "length of the function" is `2`.
 
-What about arrays? They're pretty native to JS, so are they a special type?
+What about arrays? They're native to JS, so are they a special type?
 
 ```js
 typeof [1,2,3] === "object"; // true
@@ -136,7 +136,7 @@ The `typeof` operator always returns a string. So:
 typeof typeof 42; // "string"
 ```
 
-The first `typeof 42` returns `"number"`, and then `typeof "number"` is `"string"`.
+The first `typeof 42` returns `"number"`, and `typeof "number"` is `"string"`.
 
 ### `undefined` vs "undeclared"
 
@@ -157,7 +157,7 @@ typeof b; // "undefined"
 typeof c; // "undefined"
 ```
 
-It's tempting for most developers to think of the name "undefined" and think of it as a synonym for "undeclared." However, in JS, these two concepts are quite different.
+It's tempting for most developers to think of the word "undefined" and think of it as a synonym for "undeclared." However, in JS, these two concepts are quite different.
 
 An "undefined" variable is one that has been declared in the accessible scope, but *at the moment* has no other value in it. By contrast, an "undeclared" variable is one that has not been formally declared in the accessible scope.