Stimulus (noun)

1. Something that incites to action.
2. Something that rouses or incites to activity.
3. An event, action, or influence that helps to begin or to cause something to happen.

Origin:

Late latin, from latin, goad, stimulus, from stīmulus, from stīmulāre, to urge on, from stīmus, goad.

Examples:

1. The stimulus package provided by the government helped revive the economy.
2. An increase in taxes is a stimulus to the economy.
3. The stimulus of the new equipment helped improve the company's productivity.
4. The sudden noise was a stimulus for the dogs to bark.
5. The stimulus of a new challenge is what the athlete needed to perform better.