Many people are confused about the difference between affect and effect. Before going any further, remember that “affect” is almost always a verb, whereas “effect” is more commonly used as a noun.

Affect and effect are used as follows :

  • AFFECT :
    Affect is most often used as a verb meaning ‘to have an impact’, ‘to change’ or ‘to alter’.
      • Nutrition affects our health.
      • His attitude affected the atmosphere in the office.
      • Severe flooding affected many regions.
      • The snow storm affected air traffic.
      • Public protests did not affect the government’s decision.
      • Thousands of people will be affected by the proposed changes.
      • Living in such a dark place affected his eyesight.

    Affect also has another, less-used, meaning: ‘to put on a false show of’ or ‘to pretend’:

    • She affected indifference although she was very upset.
      (= she pretended that she did not care)
  • EFFECT :
    Effect is most often used as a noun meaning ‘a result’, ‘a consequence’ or ‘an influence’.
    The expression ‘have an effect on’ is often used.
    • His words produced the desired effect.
    • Her warning had no effect on the children.
    • The effect on the economy was disastrous.
    • The medication will not have an immediate effect.
    • Music often has a soothing effect on people.

    Effect can also be used as a verb meaning ‘to bring about’, ‘to make something happen’
    or ‘to put into operation’. The use of effect as a verb is usually found in formal contexts.

      • The firm effected  the transition to computerised accounting last month.
      • The bank was requested to effect  the transfer of funds immediately.

    Effects [plural] can also mean ‘personal property or possessions’.

    •  Personal effects should be packed separately.

In most everyday contexts it is safe to remember that ‘to affect’ =  ‘to have an effect on’.
Affect is related to action whereas effect is related to consequence or result.