Filmmaking / Directing : Based on, Adapted from, or Inspired by? by Gary Tucker

Hello Stage 32 family! I have a question, I have tried to look up the answer online and the results are a tad vague, so I thought I might ask anyone here who has had experience with this or is a entertainment legal person. I am very early development phase for a bio pic about a star that left us too early. Now I have contacts that knew this person very well, family members, etc. etc., but I found about a biography written about this person that potentially could be the foundation in which a screenplay can be created. But when not doing a documentary based upon a book, what is the proper phrase when giving credit back to the source material? Thanks and I look forward to your responses!