Board Thread:Questions and Answers/@comment-3075077-20170610130349/@comment-24851456-20170611022936

Technically, it's anything that you can express thought about and exist in your mind, whether it is related to something that actually exists or not. But it needs to exist at least in your mind. Centaurs don't exist (at least not in this world) but you can think the concept of a centaur and have thoughts about it. Freedom or love are not exactly existing things but rather concepts that we, humans, have created and can share thoughts on. Either the centaurs or freedom are determined by a set of characteristics (it's an human torso on the top of a horse's body, it's a special feeling for someone), but they're not only that set of separated characteristics, they're one particular things that we can think about by conceptualizing it in our mind (rather than visualizing it, since it doesn't exist or doesn't even have a form).