Effect and Affect
An effect (noun) is a result.
The medicine had no effect.
The medicine did not work.
To effect (verb) means to bring about a result.
The manager hoped the meeting would effect a change in employee behaviour.
The manager hoped the meeting would cause the employees to change their behaviour.
To affect means to influence or to make a difference to something.
Sam's illness began to affect his work.
Sam's illness changed how he worked.