noun

reaction

A response to something or a process in which substances change chemically.

Her reaction to the surprise is a smile of delight.

Etymology

The word names an action in return. It covers a person’s response and the changes produced when substances act upon one another.

More examples

  • Peanuts can cause a severe allergic reaction.
  • Mixing vinegar and baking soda produces a chemical reaction.
  • The proposal draws mixed reactions from the staff.

Forms

reaction · reactions

react verb — Respond to something or undergo chemical change.

Similar words

response
Fits behavioral or bodily reactions, but not chemical processes.
reply
Specifically a spoken or written answer, rather than any reaction.