Nouns

(n)leaning, propensity, tendencyan inclination to do something“he felt leanings toward frivolity”
(n)proclivity, propensity, leaninga natural inclination“he has a proclivity for exaggeration”
(n)aptness, propensitya disposition to behave in a certain way“the aptness of iron to rust”, “the propensity of disease to spread”