Affect Vs Effect

Affect (transitive verb)

to cause an effect upon

Effect (transitive verb)

to bring into being, to cause

Effect (noun)

something that inevitably follows an antecedent (as a cause or agent)

To affect something is to cause it to change in some way. To effect something it to cause it to come into being. Effecting a change affects the changed thing with an effect. What could be more clear?

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From Strunk, William, Jr. and White, The Elements of Style, V. WORDS AND EXPRESSIONS COMMONLY MISUSED:

Effect. As noun, means result; as verb, means to bring about, accomplish (not to be confused with affect, which means "to influence").

As noun, often loosely used in perfunctory writing about fashions, music, painting, and other arts: "an Oriental effect;" "effects in pale green;" "very delicate effects;" "broad effects;" "subtle effects;" "a charming effect was produced by." The writer who has a definite meaning to express will not take refuge in such vagueness.

-- StevenNewton

Affect is also used as a noun in psychology, meaning, roughly, "reaction". "The patient received the bad news without affect." "Flat affect" and "neutral affect" are fancy ways of saying "emotionless."