propensity

Noun

• a disposition to behave in a certain way
  • the aptness of iron to rust
    
  • the propensity of disease to spread
    

• a natural inclination
  • he has a proclivity for exaggeration
    

• an inclination to do something
  • he felt leanings toward frivolity
    

Related words

• Synonyms: 
  aptness , proclivity , leaning , tendency