Affect and Effect are often a source of difficulty because both verbs imply the production of an effect and take as their corresponding noun the same word, effect.
Affect, the verb (see AFFECT), distinctively implies the action or operation of an agency rather than of an agent; it therefore means to influence.
- moisture affects steel
- high prices affect our pocketbooks
- the climate has affected his health
Effect, the verb (see PERFORM), implies the achievement of an end in view, and requires as its subject an intelligent agent or the means he uses to attain his end: it therefore means to bring about.
- the prisoners effected their escape
- the new system of accounting will effect a reduction in costs
Since the noun effect may be applied to any result whether brought about unconsciously or consciously, it serves equally well whether it names a result of the influence of one thing upon another or of directed effort.