Reaction has had a meteoric career, almost rivalling that of reaction and target. It now seems to come naturally to an official writer, answering an enquiry where certain equipment can be bought, to end his letter:
Would you therefore communicate with the XY Co. Ltd., and let me have your reaction.
Reaction may be properly used as a technical term of chemistry (the response of a substance to a reagent), of biology (the response of an organ of the body to an external stimulus), or of mechanics ("to every action there is an equal and opposite reaction"). One would think that was as much work as a word could reasonably be asked to do. Its present vogue is grievous. A word that connotes essentially an automatic rather than an intellectual response is being used habitually to replace such words as opinion, views, or impression. Never say "What is your reaction to this proposal?" instead of "what do you think of this proposal?" unless you wish to imply that the person you are questioning must answer instantly without reflection. Reaction's extension of its meaning was harmless at first, and even useful. One cannot quarrel with:
I suggest that Mr. X communicates with some of the firms named with a view to testing market reactions to his products.
But the further encroachments of the word should be discouraged because they blur exactitude of meaning.
The preposition after reaction must be to, never on. It is permissible to say "His reaction to your letter was unfavourable". But it is not permissible to say "Your letter had an unfavourable reaction on him". To say that is to imply a belief that one of the meanings of reaction is effect.