Mainspring

1.

(principal spring in a mechanism, impelling cause) ផ្លូវសំខាន់, កម្លាំងសំខាន់

1.

The principal or most important spring in a piece of mechanism, especially the moving spring of a watch or clock or the spring in a gunlock which impels the hammer. Hence: The chief or most powerful motive; the efficient cause of action.