Hatches vs Wagons: What's the difference?

[Nerdsrock22]

So me and my roommate were driving home from Florida the other day, looking at cars, and trying to figure out what makes a 4 door hatch and what makes a wagon.

Maybe it's just in my head, but I feel like there is a difference, he doesn't.

Example of four door hatches (imho):
http://www.caranddriver.com/var/ezwebin_site/storage/images/reviews/hot_lists/high_performance/evo_wrx_zone/2008_subaru_impreza_wrx_sti_road_test/2008_subaru_impreza_sti/2008_20subaru_20impreza_20wrx_20sti_20_65/1158467-1-eng-US/2008_20subaru_20impreza_20wrx_20sti_20_65_gallery_ image_large.jpg

http://dabigleap.files.wordpress.com/2009/05/hondafit1.jpg

http://z.about.com/d/cars/1/7/u/Q/1/09yaris5d_side.jpg

Wagons:

http://carphotos.cardomain.com/ride_images/3/519/3181/26296590002_large.jpg

http://drcarfinder.com/wp-content/uploads/2008/09/2004-volvo-wagon-v2.jpg

http://www.webwombat.com.au/motoring/news_reports/images/mitsubishi-lancer-wagon-1.JPG

I know it has to be something in the proportions (is it just rear overhang?), but what gives? :???:

[punkr6]

now you have me confused wtf....

[alpine_aw11]

I guess by definition 4 door hatches are smaller maybe? They generally have less trunk space, and less interior room. I guess the size of the car is the difference. If that's not it I'm fucking stumped.