“Efficient" is used to refer to people if they work without wasting time or energy and in a well-organized manner. The clerk who does his job well is an “efficient" worker. An inefficient clerk often messes up things, forgets a lot, loses documents and fails to complete his assignments in time. A properly working machine or system is also called “efficient".
“Effective", on the other hand, is used to mean something if it solves a particular problem that we have, or gets the desire result. It is also used for matching garments.
1. Mary is an efficient secretary and runs the office quite well.
2. Economics says that cent percent efficiency is never achievable.
3. Your prescription was very effective; my disease has been cured in a single day!
4. A wide belt would look effective with that trouser.