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2) more clearly - the difference between use and usage when they are used without article, (1)-- the difference is not related to countability. In language, usage is established use; use is pragmatic usage.  Actually, however, they are cavalierly mixed by most writers (including me).
And, of course, Mr Google (best friend of the English language learner) has more than you would want to read here

The quote is from one of the Google hits.