Say "use" rather than "usage" in the syntax index

In each table in the syntax index, we have some bit of syntax on the
left and then on the right we have features in which that bit of
syntax is used.  Should we title the column on the right "use" (or
maybe "uses") or "usage"?

One could almost, superficially, make a case for "usage".  As relevant
here, Webster's defines it as "the way in which a word, phrase,
etc. is used to express a particular idea".  That sounds close.

The trouble is that it's nearly the wrong way around.  The "idea" here
is actually the thing on the right.  The "usage" would be the place or
way in which the syntax is used to express that idea.

Conversely, definitions of "use" apply cleanly: to "employ for or
apply to a given purpose", "an instance or way of using", etc.

As Garner says:

> Whenever *use* is possible, *usage* shouldn't appear.

Let's say "use".

Author: traviscross

src/syntax-index.md

@@ -4,8 +4,8 @@ This appendix provides an index of tokens and common forms with links to where t
 
 ## Keywords
 
-| Keyword       | Usage |
-|---------------|-------|
+| Keyword       | Use |
+|---------------|-----|
 | `_`           | [wildcard pattern], [inferred const], [inferred type], [placeholder lifetime], [constant items], [extern crate], [use declarations], [destructuring assignment] |
 | `abstract`    | [reserved keyword] |
 | `as`          | [extern crate][items.extern-crate.as], [use declarations][items.use.forms.as], [type cast expressions], [qualified paths] |
@@ -66,8 +66,8 @@ This appendix provides an index of tokens and common forms with links to where t
 
 ## Operators and punctuation
 
-| Symbol | Name        | Usage |
-|--------|-------------|-------|
+| Symbol | Name        | Use |
+|--------|-------------|-----|
 | `+`    | Plus        | [addition][arith], [trait bounds], [macro Kleene matcher] |
 | `-`    | Minus       | [subtraction][arith], [negation] |
 | `*`    | Star        | [multiplication][arith], [dereference], [raw pointers], [macro Kleene matcher], [glob imports] |
@@ -117,8 +117,8 @@ This appendix provides an index of tokens and common forms with links to where t
 
 ## Comments
 
-| Comment  | Usage |
-|----------|-------|
+| Comment  | Use |
+|----------|-----|
 | `//`     | [line comment][comments] |
 | `//!`    | [inner line comment][comments] |
 | `///`    | [outer line doc comment][comments] |
@@ -128,8 +128,8 @@ This appendix provides an index of tokens and common forms with links to where t
 
 ## Other tokens
 
-| Token        | Usage |
-|--------------|-------|
+| Token        | Use |
+|--------------|-----|
 | `ident`      | [identifiers] |
 | `r#ident`    | [raw identifiers] |
 | `'ident`     | [lifetimes and loop labels] |
@@ -146,24 +146,24 @@ This appendix provides an index of tokens and common forms with links to where t
 
 ## Macros
 
-| Syntax                                     | Usage |
-|--------------------------------------------|-------|
+| Syntax                                     | Use |
+|--------------------------------------------|-----|
 | `ident!(…)`<br>`ident! {…}`<br>`ident![…]` | [macro invocations] |
 | `$ident`                                   | [macro metavariable] |
 | `$ident:kind`                              | [macro matcher fragment specifier] |
 | `$(…)…`                                    | [macro repetition] |
 
 ## Attributes
 
-| Syntax     | Usage |
-|------------|-------|
+| Syntax     | Use |
+|------------|-----|
 | `#[meta]`  | [outer attribute] |
 | `#![meta]` | [inner attribute] |
 
 ## Expressions
 
-| Expression                | Usage |
-|---------------------------|-------|
+| Expression                | Use |
+|---------------------------|-----|
 | <code>\|…\| expr</code><br><code>\|…\| -> Type { … }</code> | [closures] |
 | `ident::…`                | [paths] |
 | `::crate_name::…`         | [explicit crate paths] |
@@ -204,8 +204,8 @@ This appendix provides an index of tokens and common forms with links to where t
 
 [Items] are the components of a crate.
 
-| Item                          | Usage |
-|-------------------------------|-------|
+| Item                          | Use |
+|-------------------------------|-----|
 | `mod ident;`<br>`mod ident {…}` | [modules] |
 | `use path;`                   | [use declarations] |
 | `fn ident(…) {…}`             | [functions] |
@@ -224,8 +224,8 @@ This appendix provides an index of tokens and common forms with links to where t
 
 [Type expressions] are used to refer to types.
 
-| Type                                  | Usage |
-|---------------------------------------|-------|
+| Type                                  | Use |
+|---------------------------------------|-----|
 | `bool`, `u8`, `f64`, `str`, `…`       | [primitive types] |
 | `for<…>`                              | [higher-ranked trait bounds] |
 | `T: TraitA + TraitB`                  | [trait bounds] |
@@ -253,8 +253,8 @@ This appendix provides an index of tokens and common forms with links to where t
 
 [Patterns] are used to match values.
 
-| Pattern                           | Usage |
-|-----------------------------------|-------|
+| Pattern                           | Use |
+|-----------------------------------|-----|
 | `"foo"`, `'a'`, `123`, `2.4`, …   | [literal patterns] |
 | `ident`                           | [identifier patterns] |
 | `_`                               | [wildcard pattern] |