Why is the suffix -tion pronounced shun?

Answer 1

"Tion" is pronounced "shun" because of Mr. Noah Webster who created the first dictionary of English for the American People.

A little history: He noticed that the people living in the new nation of United States spoke very differently from each other - so different that often times there were misunderstanding that resulted in violence. He was determined to remedy this situation by giving Americans a 'mother tongue' of their own.

To that end he traveled the land listening and writing down pronunciations of various words and standardizing them and publishing them - thus encouraging the way the words were pronounced and spelled.

For example: he changed the word "musik" to music and the word "plough" to "plow" and the word "centre" to "center". He wanted to change the word "women" to "wimmen" and the word "tongue" to "tung" - but people hung to the old versions of those words and he had to give in.

Now why is "tion" pronounced "shun". Mr. Webster found that people were pronouncing words with "tion" like "salvation" like this "sal VA she un". He suggested it would better to pronounce it as "sal VA shun". People found that easier to say and began do that with all the "tion" words.

Note that the old pronunciation of "tion" sort of followed the romance languages until Mr. Webster's involvement. For example the same word "salvation" in Spanish is written as "salvación" and pronounce "sal va see ON".

Latin in the origin of the 'tion words. The original form of the word was "salvatio" and is pronounced "sal va TSEE io". How did it get the "n"? That would require me to explain how Latin nouns work. If curious, Google "latin nouns declensions"

Anyway as far as I can tell this is why we pronounce "tion" as "shun".

Answer 2

The suffix -tion is pronounced as "shun" because English borrowed it from Latin, where the ending "-tio" was pronounced with a "sh" sound. This pronunciation was carried over into English when the Latin words were adopted.