Student or Learner
Difference between the word Many,several and multiple, and when to use each ?
Judging by this definiton:Multiple - Definition for English-Language Learners from Merriam-Webster's Learner's Dictionary
I think they are almost complete synoyms (perhaps, "multiple" is a litle more than "several" and less than "many") but let's wait for the native speakers' opinion.
If I were a native speaker of English, I would never shut up. :-)