mainspring
noun /ˈmeɪnsprɪŋ/
/ˈmeɪnsprɪŋ/
- [usually singular] mainspring (of something) (formal) the most important part of something; the most important influence on something
- Small companies are the mainspring of the British economy.
- Her Christian faith was the mainspring of her life.
- the most important spring in a watch, clock, etc.