Why "alternate"and not "alternative" CD?

[Douglas Pollard]

On 02/09/2012 01:07 PM, compdoc wrote:
>> With English not being my native language, I think the proper term for
>> "alternate CD" is "alternative CD". Why "alternate" is used instead?
> I think either word is appropriate. It might depend on where in the world
> the person lives as to which they use.
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Seems like to me that alternate Cd is correct. It is an alternate cd so 
is an alternative to the other.  Is one a noun and the other a verb?  Doug