A short story, a novella or a novelette?

Despite having a novel on the go already, I decided to start writing a short story as well (there will be some shameless self-publicity for this at the end of the post). This is mostly because I have been writing this novel for quite a while and I know it's not going to be finished for a long time yet - I'm only roughly halfway through the first draft! 

But after showing my new work to my Other Half, he suggested that this story could be made much longer than a short story. Knowing that I have not got the time to start a whole new novel, plus that would risk the old one being forgotten, I wondered how long a short story could really be before it becomes something else. So I turned to my old friend, Google. It turns out, a short story is generally anything below 7,500 words. More than that, and it becomes a "novelette", something I had never even heard of before. A novella, which I ignorantly thought was just another, more fancy way of saying short story, is anything above 17,500 words. I had no idea that literary genres were so complicated! 

If you're interested in reading the first part of my short story, it can be found here: http://ameliaappletree.wordpress.com/2012/08/14/short-story/