Concepts may be decomposed into a set of features. Features from various different concepts can then be mixed and matched to define new concepts. If the new concepts prove useful in describing the world they are retained in the pool of known patterns.
It's quite common to see a new concept formed from an old one by the simple addition of a single new feature:
horse concept + horn feature = unicorn concept
horse concept + wing feature = Pegasus concept
man concept + wing feature = angel concept
I see Asa H doing this as well.