Affect is the standard verb meaning to influence — the delay affected the schedule. Impact as a verb means the same thing to many writers, but it is one of the most objected-to usages in business English. The safe advice: use affect for the verb and impact for the noun.
The core difference
One is uncontroversial; the other is disputed as a verb.
- affect (verb) — influence: it affected the outcome.
- impact (noun) — an effect or collision: a significant impact.
- impact (verb) — disputed: it impacted the outcome.
Why the objection exists
Impact as a verb originally meant to strike forcefully or to pack tightly — an impacted tooth. The "affect" sense spread through business and management writing, and to many readers it still signals jargon rather than precision. The objection is about register more than grammar.
The practical advice
Affect costs nothing and offends nobody. If you want a stronger word, influence, damage, improve or disrupt all say more than impact does anyway — which is the better argument against it.
The other pair
Do not confuse this with affect versus effect: affect is normally the verb, effect the noun.
Frequently asked questions
Is "impacted the results" wrong?
Not grammatically, but it is widely objected to as jargon. Affected is the safer choice.
When is impact uncontroversial?
As a noun — a significant impact — and in its original verb sense of striking forcefully.
What is a better alternative?
Affect, or a more specific verb such as damage, improve or disrupt, which say more than impact does.