His ambition is to run his own business.
He has already achieved his main ambition in life - to become wealthy.
Learning English is one of my ambition[s]. (Preliminary English Test; B1; Farsi)
My sister always had more ambition than I did.
Love, hate, ambition and fear [of] losing are the main subjects for Orson Well[e]s and Tim Burton, the directors [of these two films]. (First Certificate in English; B2; Spanish)