Can lenses made by any brand fit onto any cameras if they are the right size?

Hi, I'm looking to buy a Sony A200 as a starter dslr, but am wondering about which lenses I can buy. The kit lens (18-70mm) that comes with it will be fine to start with I'm sure, but I also want to buy a prime lens. This will probably be the Minolta 50mm 1.7. I was just wondering if lenses by other... show more Hi, I'm looking to buy a Sony A200 as a starter dslr, but am wondering about which lenses I can buy. The kit lens (18-70mm) that comes with it will be fine to start with I'm sure, but I also want to buy a prime lens. This will probably be the Minolta 50mm 1.7. I was just wondering if lenses by other manufacturers eg Canon, Nikkon will fit the A200. I know that most Minoltas and Sonys will but I don't get how to work out if others will. Is there a certain size I need to look out for and if so, can you buy adapters so that other lenses will fit? Also, I'm not sure about whether I can use manual focus lenses with the A200 as it's autofocus. The lens I'm planning on getting is AF and I know it will work, but the manual seems to be way cheaper?
Thanks
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