Common Mistakes : Efficient

adjective

.BAD: The medicine proved very efficient
.GOOD: The medicine proved very effective

.BAD: We need more efficient ways of dealing with pollution or the problem will get worse
GOOD: We need more effective ways of dealing with pollution or the problem will get worse

: efficient = working quickly and without waste
.The more efficient the engine, the less petrol it uses
.Since the new software was installed, library services have become much more efficient

: effective = having the desired effect
.There are many effective ways of using computers for training purposes
.The advertisement was simple, but remarkably effective