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Hello,

Please clarify when to use 'depending upon' and 'depending on'? Also, how do they differ from 'depend upon' and 'depend on'?
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They are interchangeable and synonymous, with upon only slightly more formal.
Comments  
I would use "depending on" or "dependent upon."
While, theoretically, no combination is incorrect when spoken or written, "depending upon" is too informal for the latter. Use "dependent upon," instead.