Example One :- a) principal and b) principle
Example Two :- a) affect and b) effect

It would be nice , if sentences are used to explain the full meanings of the words.

Can you give more examples.

Hi, ROLCAM!

Are you having difficulty finding the differences between these words by performing a search for them?

Thanks!

HI CLOUGH,

Not at all !
I invariably come across these quite often in reading other people's material.
From the use of these words , I was able to know who wrote the communications in a place I previously worked.
There must be quite a number of
People that have had difficulties with these type of pairs..
I just wondered how much more difficult English is for non speaking
Mortals.
You see English was not my first language for the first 20 years of my life.

Try here:
http://www.yourdictionary.com/examples/principle