Mainspring

Definitions

1. The principal spring of a clockwork mechanism, which drives it by uncoiling.
2. The most important reason for, or element of, something.
   figuratively

Equivalents

Examples

“He was wise, for he had seen a long succession of mechanical toys arrive⟳ to boast and swagger, and by-and-by break⟳ their mainsprings and pass⟳ away.”

“My daughter is the mainspring of my life.”

“But in the England of Shakespeare’s history plays, the mainspring of the system has broken down.”

CEFR level