reaction-n; 5 Senses

Sense Number 1: (chemistry) a process in which one or more substances are changed into others.

Commentary: REACTION[+event][+chemistry]

There was a chemical reaction of the lime with the water.
The reaction caused an explosion.

WordNet 3.0 Sense Numbers: 1

Sense Number 2: An intellectual or emotional response to a stimulus.

Commentary: REACTION[+mental][+event]
NOTE: may include additional physical responses, but must include an element of judgement.

His reaction to the news was to make a plan.
He was please by the audience's reaction.
John feared his mother's reaction to the broken lamp.

WordNet 3.0 Sense Numbers: 2, 5

Sense Number 3: A bodily process occurring due to the effect of some antecedent stimulus or agent.

Commentary: REACTION[+physical][+event]

He had a bad reaction to the medicine.
His reactions have slowed with age.

WordNet 3.0 Sense Numbers: 3

Sense Number 4: (mechanics) the equal and opposite force that is produced when any force is applied to a body.

Commentary: REACTION[+mechanics]

Every action has an equal and opposite reaction.

WordNet 3.0 Sense Numbers: 4

Sense Number 5: Something done in opposition to something else (policially or socially).

Commentary: REACTION[+opposite][+event]

His style of painting was a reaction against cubism.
The forces of reaction carried the election.

WordNet 3.0 Sense Numbers: 6, 7