Use - usage
Linguists and teachers of language often seem to use these two nouns almost as if they were interchangeable. In practice, their meaning is very close, and different writers will often choose differently in similar contexts.
There is a rule of thumb that AWE can suggest to help you make up your mind between them (if you are a student trying to write accurately), or help you understand the idiom if you are learning English as a foreign language. It is this: the noun use is more particular, referring more often to a single event. Usage refers more to repeated uses, to a pattern that is more habitual. "British usage of words to do with cars differs from the American usage of terms to do with autos", for example; but "His use of the word decimate is different from mine."
(Notice the pronunciation difference between the noun use, with an '-s-' sound, IPA: /ju:s/, and the verb to use, where the sound is a '-z-', IPA: /ju:z/. Technically speaking, the first is unvoiced, the latter voiced.)