Addressing comments

This attempts to use `document` in its various forms when discussing the artifact (replaces `file` in the most part), though I tried to avoid mixing the file-like instances with the API documentation ones. Some instances have been changed to use `define` (or similar forms), though based on the comments suggesting that both `definition` and `description` are used in common parlance, `description` has not been fully expunged—hopefully this is a reasonable middle ground, but if upon review there is strong support for that, I'll re-submit.

Author: earth2marsh

versions/3.0.md

@@ -8,9 +8,9 @@ This document is licensed under [The Apache License, Version 2.0](http://www.apa
 
 ## Introduction
 
-The OpenAPI Specification (OAS) defines a standard, language-agnostic interface to RESTful APIs which allows both humans and computers to discover and understand the capabilities of the service without access to source code, documentation, or through network traffic inspection. When properly documented, a consumer can understand and interact with the remote service with a minimal amount of implementation logic.
+The OpenAPI Specification (OAS) defines a standard, language-agnostic interface to RESTful APIs which allows both humans and computers to discover and understand the capabilities of the service without access to source code, documentation, or through network traffic inspection. When properly defined, a consumer can understand and interact with the remote service with a minimal amount of implementation logic.
 
-An OpenAPI document can then be used by documentation generation tools to display the API, code generation tools to generate servers and clients in various programming languages, testing tools and many other use cases.
+An OpenAPI definition can then be used by documentation generation tools to display the API, code generation tools to generate servers and clients in various programming languages, testing tools, and many other use cases.
 
 ## Table of Contents
 <!-- TOC depthFrom:1 depthTo:3 withLinks:1 updateOnSave:1 orderedList:0 -->
@@ -67,7 +67,7 @@ An OpenAPI document can then be used by documentation generation tools to displa
 ## Definitions
 
 ##### <a name="oasDocument"></a>OpenAPI Document
-A document or set of files that document an API. An OpenAPI document uses and conforms to the OpenAPI Specification.
+A document (or set of documents) that define or describe an API. An OpenAPI document uses and conforms to the OpenAPI Specification.
 
 ##### <a name="pathTemplating"></a>Path Templating
 Path templating refers to the usage of curly braces ({}) to mark a section of a URL path as replaceable using path parameters.
@@ -127,13 +127,11 @@ In order to preserve the ability to round-trip between YAML and JSON formats, YA
 - Tags MUST be limited to those allowed by the [JSON Schema ruleset](http://www.yaml.org/spec/1.2/spec.html#id2803231).
 - Keys used in YAML maps MUST be limited to a scalar string, as defined by the [YAML Failsafe schema ruleset](http://yaml.org/spec/1.2/spec.html#id2802346).
 
-**Note:** While APIs may be described by OpenAPI documents in YAML or JSON format, the API request and response bodies and other content are not required to be JSON or YAML.
+**Note:** While APIs may be defined by OpenAPI documents in either YAML or JSON format, the API request and response bodies and other content are not required to be JSON or YAML.
 
 ### <a name="documentStructure"></a>Document Structure
 
-An OpenAPI document MAY be made up of a single document.
-However, parts of the document MAY be split into separate files, at the discretion of the user.
-This is applicable for `$ref` fields in the specification as follows from the [JSON Schema](http://json-schema.org) definitions.
+An OpenAPI document MAY be made up of a single document or be divided into multiple, connected parts at the discretion of the user. In the latter case, `$ref` fields MUST be used in the specification to reference those parts as follows from the [JSON Schema](http://json-schema.org) definitions.
 
 It is RECOMMENDED that the root OpenAPI document be named: `openapi.json` or `openapi.yaml`.