The only difference is that “pronounciation” is wrong and “pronunciation” is correct. Whichever you say, you will be understood. Some people will snigger and belittle you if you use the wrong word.
What do Brits call convenience stores?
Corner shop
Why do we call groceries groceries?
A grocer in medieval England was a wholesaler, and the name is derived from an Anglo-French word having the same meaning, groser. ... The first known use of the word grocery was in the 15th century, and it referred to the goods sold by a grocer.