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1.What is the word to describe something in the middle? Is it long or short? It is middle-sized (?). -
- I'm not sure what you are looking for-- an adjective for an item of intermediate size or position? Here are some: middle-sized, intermediate, central, moderate, medial.2. What do you say the word 'super' is - a prefix? Is that why it is hyphenated?--
Yes, it is a prefix, and it is followed by a hyphen in your example (super-job) but needn't be (supervisor). In your sentence, however, I suspect that what is meant is super job (no hyphen), where super is an independent word, slang meaning 'an article of a superior quality, grade, size, etc.'.