The phrase "affirmative action" does not tell you what it is about. Even though the literal meaning of this phrase can be very broad (in theory it could be referring to affirmative action of achieving anything), but it is commonly used to refer to a very specific kind of affirmative action. What really matters is the specifics, which is the core meaning of the phrase but not captured within the phrase. For someone who does not know the context of the discussion, the phrase can be very confusing.
It is kind of like using the word "dog" refer to a specific kind of dog. And then in the whole public discussion of that specific kind of dog, it never has a specific name, just called "dog". This is not a good example, but hope you know what I mean.
Is there a linguistic term for this kind of phenomenon? What are the other examples of this kind of usage?