Как по Английски будет служить причиной

noun

A reason for doing something.

Примеры использования:

Police were unable to establish a motive for his murder

adjective

Producing physical or mechanical motion.

Примеры использования:

The charge of gas is the motive force for every piston stroke

adjective

Of a person, action, etc.: provided with or having a motive; enthusiastic, motivated.

verb

Provide (someone) with a reason for doing something.

Примеры использования:

He was primarily motivated by the desire for profit