How many simple machines are there?

Although everybody seems to know about all the simple machines, when I started teaching this unit I still had to look it up to make sure I have all of them. I tested my husband to see if he remembered all of the machines, and although usually he has a great memory, this time he remembered only four of the (six? seven?). Try it yourself...

To know all about the simple machines, I had to research them (mostly online). It's funny, because all the sites and books I looked at, the author usually states there are SIX simplse machines. Yet many of the sites contradict each other as to which machines are the SIX simple machines. Here is my count (and I count seven):

1. Lever
2. Incline Plane
3. Pulley
4. Wheel and Axel
5. Screw
6. Wedge
7. Gears

Some of the sites don't include the wedge, as it's pretty much an incline plane. But then I would say that the screw is also the same as an incline plane, right? And what about the wheel and axel - that's like a lever that never stops lifting, right? And a gear is like a wheel and axel or a pulley. On other sites, gears are not part of the "simple machines" list. And even other sites don't have the screw. What's up with that?

I wish we had better textbooks, because even our grade eight text book doesn't have a complete list. Since our textbook (although pretty, colourful and at times very interesting) is not a good resource, I need to look elsewhere, and elsewhere is not always trustworthy.

Anyway, I wish there was an official list that I could go by (I'm really into lists and organization). For now, I'm going with my seven.