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stimulus

STIM-yuh-luss /ˈstɪm.jə.ləs/

nounB2GRESATTOEFLMCAT

academicscientific

A thing or event that evokes a specific functional reaction in an organ, tissue, or psychological state.

Serves as the initial trigger in a stimulus-response loop.

The story behind the word. In ancient Rome, a 'stimulus' was a pointed wooden goad or spike used by farmers to prick oxen to make them move faster. In the 18th century, physiologists adopted the term for any sensory poke that causes an organism to react.

Word relationships

catalyst: Catalyst accelerates an existing reaction, while stimulus directly provokes a reaction.
incentive: Incentive is a future goal or reward; stimulus is an immediate sensory or physical trigger.

deterrent: Deterrent discourages or prevents action.
suppressant: Suppressant dulls or stops physical or emotional responses.

Commonly confused with

stimulant: A stimulant is a substance (like caffeine) that increases physiological activity; a stimulus is any sensory trigger.

Word family

stimulate (verb): To raise levels of physiological or nervous activity.
stimulation (noun): The raising of vigor, action, or energy.

Collocations

external stimulus
conditioned stimulus
stimulus-response
sensory stimulus

Idioms & expressions

catalyst for action

Example sentences

"A sudden flash of light acts as a visual stimulus that triggers rapid pupil contraction." Neuroscience
"The government provided a financial stimulus to encourage consumer spending during the downturn." Economics

Memory hook

STIMulus STIMulates you like a sharp prick. A pointy goad poking you to action.

When not to use

Note the plural form: use 'stimuli', never 'stimuluses'.

Fun facts

In psychological experiments, a 'supernormal stimulus' is an exaggerated fake trigger (like a massive artificial egg) that animals prefer over real ones!