basing
v.v. to use something as the main idea or starting point for a new thing. You use this when you build a story, a plan, or an opinion on a specific fact.
v. the present participle of 'base'; refers to the act of using a particular fact, situation, or place as the foundation for something else. Often used in the passive voice followed by 'on' or 'upon'.
I am basing my report on the latest sales figures.
The director is basing the movie's plot on a true story from the nineteenth century.
By basing their entire economic strategy on a single volatile commodity, the government left the nation vulnerable to sudden shifts in global market demand.
Typically followed by the preposition 'on' or 'upon'.
basing in a true storybasing on a true storyWhen 'base' means to use something as a foundation for an idea, it requires the preposition 'on', not 'in'.