A propensity is a strong natural tendency to do something.

// As a child, she had a strong propensity for mischief.

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"The work suggests that the propensity for the cleverest AI chatbots to go off the rails isn’t just a quirk that can be papered over with a few simple rules." — WIRED, 1 Aug. 2023

If you’re partial to picking synonyms of propensity, perhaps peruse the letter "p," which predominates for such words, in our pages. Proclivity, preference, penchant, and predilection all share with propensity the principal meaning of "a strong instinct or liking." Propensity comes from Latin prōpensus, a form of prōpendēre, a verb meaning "to incline" or "to hang down" (as pendulous things do). With that in mind, it’s perfectly plausible that leaning and inclination are as good synonyms of propensity as any of those "p"-words.