Synonyms for Ought:

n.

may, Cannot, can, used to, could, might. charge (noun)
must, need.
ought (noun)
must, had better, should, need.

v.

have (verb)
should.

Other synonyms:

Cannot. used to. could, may. might. can. Other relevant words:
may, could, Cannot, must.

Usage examples for ought

  1. I don't know anything at all that I ought to know." – Rose of Dutcher's Coolly by Hamlin Garland
  2. She ought to stay. – The Dynasts An Epic-Drama Of The War With Napoleon, In Three Parts, Nineteen Acts, And One Hundred And Thirty Scenes by Thomas Hardy
  3. Well, said I, if you believe him, you ought to know. – The Professor's Mystery by Wells Hastings Brian Hooker