The Difference Between Villains and Antagonists

Oftentimes, the words "villain" and "antagonist" are used interchangeably, and there's good reason for this (which I will talk about it just a moment). However, they do not mean the same thing, and this is where some writers get tripped up.

Image found at http://undertheivy.tumblr.com/page/44. It is not mine.

I had to figure out the difference for myself a while back, when I realized that while my main character (Mara) for Shadows and Light was a villain, she wasn't an antagonist. Likewise, her counterpart and new partner main character (Ace) was an antagonist, but not a villain. I'd like to explain how this is possible.
First, let's start with the google dictionary definitions of the two terms:

Look at those little highlighted phrases (Paint does such a nice, clear job, doesn't it?). Antagonists are characterized by simple opposition. An antagonist is not necessarily evil, he merely has opposing actions, thoughts, motives, etc. to (in a story) the protagonist. The term does not say anything at all about the actual personality of the character. It is simply a plot role.

Now villain, that's a little more intense. A villain has "evil actions or motives" and is "responsible for specified trouble, harm, or damage." A villain is bad. He may or may not actually oppose the main character - for all we know, he is the main character! "Villain" is not a plot role - it's a character type.

As I said before, the antagonist is often a villain and vice-versa. Think Voldemort of Harry Potter, Sauron of Lord of the Rings, Lord Sidious of Star Wars, the White Witch from The Lion, the Witch, and the Wardrobe, and Lady Tremaine of Cinderella. 

But sometimes, just sometimes, the two terms separate. 

Villains who aren't antagonists don't appear very often, but they exist. If they're not the antagonist, they're the protagonist (I can't think of anything where there's a villain just hanging out doing nothing towards the plot). I'm told by this post on the subject (at The Write Practice, an awesome blog) that Dexter of Dexter is such a character, along with Frank William Abagnale, Jr. of Catch Me If You Can and Megamind from Megamind. I also think of Maleficent from the recent Disney movie by the same name (she sort of starts out hero, dips into villain, and rises again, but for a time it was true) and Emperor Kuzco from The Emperor's New Groove. My own lovable Mara fits into this rare category. *cuddles her*

Also, there are antagonists who aren't villains. They oppose the protagonist, but they aren't evil. Marshall Gerard of The Fugitive, Elsa from Frozen, Shadow from Sonic X, Dr. Octopus from Spider-man 2, Doctor Curt Connors from The Amazing Spider-man, Bucky Barnes from Captain America: The Winter Soldier, and Inspector Javert from Les Miserables are a few examples. None of them are evil in their motives, but all provide a major conflict with the protagonist. A lot of these characters are brain-washed, manipulated, or enforcing the law. I have an antagonist like this: High General Keir Durjaya from Taken.

So to recap, villains are:

1. Evil. They have evil motivation and evil actions to match.
2. Aren't necessarily opposed to the protagonist. In fact, they can be a protagonist. 
3. "Villain" is a character type, not a plot role. 

Antagonists are:

1. Not necessarily evil. The can actually be really decent guys who just happen to have a conflicting agenda with the protagonist.
2. Opposed to the protagonist. They cause conflict with the story's main character.
3. "Antagonist" is a plot role and doesn't say anything about the character's personality or motivations.

I hope that helps anyone who was struggling with the definitions. This can all get very confusing! Especially when you start trying to disentangle villains from anti-villains, or tread into the murky ground surrounding protagonists, heroes, and anti-heroes! I'm going to tackle the difference between protagonists and heroes next, followed by anti-villains and anti-heroes, so stick around. I've also got a few more book reviews coming up, since I've actually had time to read since school ended. 

Have you had any confusing situations when a villain wasn't an antagonist or vise-versa? Who's your favorite villain/antagonist and why?