reflex

Example:Hunger is an instinct that drives animals to seek food.

Definition:A natural, almost involuntary behavior that is characteristic of a particular creature or class of creatures.

Example:He acted on impulse and bought a new guitar without thinking about the financial implications.

Definition:A sudden strong desire or urge to act, often leading to an immediate response without much thought.

Example:The chemical reaction was triggered by the addition of the reagent.

Definition:A change that occurs in response to a stimulus, particularly one that is not influenced by the will or consciousness.