What exactly defines a fancharacter from an OC?

If it's in any way involved with the original story, it's a fan character. If it's made from your own original story not involving a different one that you didn't make, then it would be an OC.

--
"How are we supposed to get by a wall of gay horses?" ~Braden

So specie has nothing to do with it? Your definition is sort of vague, but I suppose it isn't any more vague than the one I give on my website article on fancharacter making.([link])

--
"I'll be famous someday, but for now I'm stuck in middle school with a bunch of morons."
-Greg Heffley
I take unlimited requests![link]

So if you create an anthro character that's based off an animal species, is it an OC or a fan character of God's handiwork?

--
"Energy drink are very effective at staving off depression. *pause* Did I say that out loud?"
-Me, in Algebra Class

"God cannot give us a happiness and peace apart from Himself, because it is not there. There is no such thing."
-C.S. Lewis

Or even Darwin's?

--
"How are we supposed to get by a wall of gay horses?" ~Braden

1. Please use the reply button.
2. I can't read the website because the background/font combination.
3. Say you create a character that is a hedgehog ,or at least in the sonic style, and happens to a be friends with with Sonic. That would be a fan character because the original story and universe were not made by you. An original character would be the hedgehog in a different style, in his own story, and this story would have nothing to do with the Sonic universe and characters. Hope that clears it up a bit.

--
"How are we supposed to get by a wall of gay horses?" ~Braden

Well, Darwin never made the animals, he simply put forth a theory on how they came about, so really it would be evolution's handiwork. But evolution is really an impersonal process, devoid of a creative mind behind the design of living things. If you believe in evolution, than it's an OC; if you believe in God, it's a fan character.

--
"Energy drink are very effective at staving off depression. *pause* Did I say that out loud?"
-Me, in Algebra Class

"God cannot give us a happiness and peace apart from Himself, because it is not there. There is no such thing."
-C.S. Lewis

it really depends on what you mean by half.

if it's half as in "3/4 copy, 1/4 personnal input" then it's a fancharacter. but if it's "inspired from, but 80% original" then it's an OC. and if it's 50/50, then the decision is yours, wether to consider it as a fanchar or not

--
Proud furry/xbox/French fanboy
l33tspeaking furry since 1674.

Personally I would say it depends on the art style and contect of the character.
If a character is in the style of an already known theme, such as Sonic, or another well known series then I would sayhat they are a Fnaharacter, as the assosiation will auomatically be made with that series. If the artwork is independant, and of the artsts own style, then I would be inclined to say that they are an Original Character.

I think italso depeds a lot on the characters story as well, but ~hoodlumd has already covered most of it.

you can place her in a environment/world created by someone else and that will make her a fan character other wise is an OC.